SEMTECH SC2443

SC2443 Dual-Phase Single or Two Output Synchronous Step-Down Controller POWER MANAGEMENT Description Features The SC2443 is a high-frequency dual synchronous step-down u Wide input voltage range: 4.7V to 16V switching power supply controller. It provides out-of-phase u 0.5V feedback voltage for low-voltage outputs high-current output gate drives to all N-channel MOSFET power u Programmable frequency up to 1 MHz per phase stages. The SC2443 operates in synchronous continuous-con- u 2-Phase synchronous continuous conduction mode for duction mode. Both phases are capable of maintaining regula- high efficiency step-down converters tion with sourcing or sinking load currents, making the SC2443 u Out-of-phase operation for low input current ripples suitable for generating both VDDQ and the tracking VTT for u Output source and sink currents DDR applications. u Fixed frequency peak current-mode control u 75mV/-110mV maximum current sense voltage The SC2443 employs fixed frequency peak current-mode con- u Inductor DCR current-sensing for low-cost applications trol for the ease of frequency compensation and fast transient u Dual outputs or 2-phase single output operation response. u Excellent current sharing between individual phases u Individual soft-start, overload shutdown and enable The dual-phase step-down controllers of the SC2443 can be u External reference input for DDR applications used to produce two individually controlled and regulated out- u External synchronization puts or a single output with shared current in each phase. The u Industrial temperature range Step-down controllers operate from an input of at least 4.7V u 4mm X 4mm X1mm 24-lead MLPQ package and are capable of regulating outputs as low as 0.5V Applications Individual soft-start and overload shutdown timer is included in each step-down controller. The SC2443 implements hiccup u Telecommunication power supplies overload protection. In single output current share configura- u DDR memory power supplies tion, the master timer controls the soft-start and overload shut- u Graphic power supplies down functions of both controllers. u Servers and base stations Typical Application Circuit VIN VIN VOUT1 VP1 VIN VIN VOUT1 VP1 VP1 VOUT1 VP1 VOUT1 U1 IN1- U1 IN1- 1 18 1 18 IN1- IN1- GDL1 IN1- IN1- GDL1 2 17 2 17 COMP1 PVCC COMP1 PVCC 3 16 VIN 3 16 VIN SYNC PGND SYNC PGND SC2443 SC2443 4 15 4 15 AGND GDL2 AGND GDL2 5 14 REF GDH2 5 14 VOUT2 REF GDH2 6 13 IN2- REFIN BST2 6 13 REFIN BST2 VIN VIN IN2- Dual Independent Outputs Single Output With Current Sharing Aug. 2008 1 7 24 COMP2 ROSC 8 23 IN2- CS1- 9 22 CS2- CS1+ 10 21 CS2+ SS1/EN1 11 20 SS2/EN2 BST1 12 19 AVCC GDH1 7 24 COMP2 ROSC 8 23 IN2- CS1- 9 22 CS2- CS1+ 10 21 CS2+ SS1/EN1 11 20 SS2/EN2 BST1 12 19 AVCC GDH1 GDH1 AVCC BST1 SS2/EN2 SS1/EN1 CS2+ CS1+ CS2- CS1- IN2- ROSC COMP2 SC2443 Pin Configuration Ordering Information Top View Device Package (1,2) SC2443MLTRT 24-lead 4mm X 4mm X mm MLPQ SC2443EVB Evaluation Board 24 19 Notes: () Available in tape and reel only. A reel contains 3,000 devices. (2) Available in lead-free package only. Device is WEEE and RoHS IN1- 1 18 GDL1 compliant. COMP1 PVCC SYNC PGND GDL2 AGND GDH2 REF REF 6 13 BST2 IN 7 12 (24-lead 4mm X 4mm X mm MLPQ) θ = 29°C/W JA Marking Information Marking for the 4 X 4mm MLPQ-24 package: 2 SC2443 Absolute Maximum Ratings Recommended Operating Conditions AVCC, PVCC Voltage …………………………… -0.3 to 20V Input Voltage Range ………………………… 4.75V to 16V V , V Voltage ……………………………… -0.3 to 32V BST1 BST2 ……………………………… - 0.3 to 40V Thermal Information (1) (for <10ns @ freq. < 500kHz) Junction to Ambient …………………………… 29°C/W Maximum Junction Temperature ……………………… 150°C SS1/EN1, SS2/EN2, SYNC Voltage ……………… -0.3 to 6V Storage Temperature ………………………… -65 to +150°C IN1-, IN2-, REF Voltage ………………… -0.3 to AVCC+ 0.3V REF , COMP1, COMP2 Voltage ………… -0.3 to AVCC+ 0.3V IN CS1+, CS1-, CS2+, CS2- Voltage ………… -0.3 to AVCC+ 0.3V PGND to AGND ……………………………………… ± 0.3V Peak IR Reflow Temperature …………………………… 260°C Exceeding the above specifications may result in permanent damage to the device or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not recommended. NOTES- (1) Calculated from package in still air, mounted to 3” x 4.5”, 4 layer FR4 PCB with thermal vias under the exposed pad per JESD51 standards. (2) This device is ESD sensitive. Use of standard ESD handing precautions is required Electrical Characteristics Unless otherwise specified: AVCC = PVCC = 12V, V = V = 12V, SYNC = 0V, -40°C < T = T < 85°C, R =51.1kW. BST1 BST2 A J OSC Parameter Symbol Conditions Min Typ Max Units Undervoltage Lockout AVCC AVCC Start Threshold AVCC rising 4.5 4.7 V TH AVCC AVCC Start Hysteresis 170 mV HYST I AVCC Operating Current 12 16 mA CC I AVCC Quiescent Current in UVLO AVCC = AVCC - 0.2V 1.7 mA q TH Channel 1 Error Amplifier Non-inverting Input Voltage V 0.49 0.5 0.51 V IN1+ Non-inverting Input Voltage V 0°C < T = T < 70°C 0.4925 0.5 0.5075 V IN1+ A J Non-inverting Input Line Regulation AVCC < AVCC < 15V 0.02 %/V TH Input Offset Voltage 1 mV Inverting Input Bias Current I -0.1 -0.25 µA IN1- -1 Amplifier Transconductance G 260 µW M1 Amplifier Open Loop Gain A 65 dB OL1 Amplifier Unity Gain Bandwidth 5 MHz COMP1 Switching Threshold V =V = 0, V Rising 2.2 V CS1+ CS1- SS1 Amplifier Output Sink Current V = 1V, V = 2.5V 16 µA IN1- COMP1 Amplifier Output Source Current V = 0V, V = 2.5V 12 µA IN1- COMP1 3 SC2443 Electrical Characteristics (continued) Parameter Symbol Conditions Min Typ Max Units Channel 2 Error Amplifier () Input Common-mode Range 0 3 V () Inverting Input Voltage Range 0 AVCC V Input Offset Voltage .5 mV Non-inverting Input Bias Current I -50 -380 nA IN2+ Inverting Input Bias Current I -00 -250 nA IN2- Inverting Input Voltage for 2 phases 2.5 V Single Output Operation -1 G Amplifier Transconductance 260 µW M2 A Amplifier Open Loop Gain 65 dB OL2 Amplifier Unity Gain Bandwidth 5 MHz COMP2 Switching Threshold V =V = 0, V Rising 2.2 V CS2+ CS2- SS2 Amplifier Output Sink Current V = 2.5V 6 µA COMP2 Amplifier Output Source Current V = 2.5V 2 µA COMP2 Oscillator f , f Channel Frequency 450 500 550 kHz CH CH2 () Synchronizing Frequency 2.f kHz CH SYNC Input High Voltage .5 V SYNC Input Low Voltage 0.5 V Channel Maximum Duty Cycle D , D 88 % MAX MAX2 D , D Channel Minimum Duty Cycle 0 % MIN MIN2 Current Limit Comparator Input Common Mode Range 0 AVCC- V V , V Cycle by cycle Peak Currentr Limit V = V = 0.5V, Sourcing 60 75 90 mV ILIM+ ILIM2+ CS- CS2- Valley Current Overload Shutdown V , V V = V = 0.5V, Sinking -85 -0 -30 mV ILIM- ILIM2- CS- CS2- Threshold Positive Current sense V = V = 0 CS+ CS- I , I -0.7 -2 µA CS+ CS2+ Input Bias Current V = V = 0 CS2+ CS2- Negative Current sense V = V = 0 CS+ CS- I , I -0.7 -2 µA CS- CS2- Input Bias Current V = V = 0 CS2+ CS2- 4 SC2443 Electrical Characteristics (continued) Parameter Symbol Conditions Min Typ Max Units Gate Drivers High side Gate Driver V , V = 2V .5 A BST BST2 Peak Source Current High side Gate Driver V , V = 2V  A BST BST2 Peak Sink Current Low side Gate Driver AVCC = PVCC = 2V .5 A Peak Source Current Low side Gate Driver AVCC = PVCC = 2V  A Peak Sink Current Gate Drive Rise Time C = 2200pF 20 ns L Gate Drive Fall Time C = 2200pF 20 ns L Low side Gate Driver to High side C = 0 90 ns L Gate Driver Non-overlapping delay High side Gate Driver to Low side C = 0 90 ns L Gate Driver Non-overlapping delay T = 25°C Minimum On Time 50 ns A Soft Start, Overload Latchoff and Enable I , I V = V = .5V Soft Start Charging Current 2 µA SS SS2 SS SS2 Overload Enabling Soft Start Voltage V and V Rising 3.2 V SS SS2 Overload IN- Threshold V = 3.8V, V falling 0.75V V SS IN- REF Overload IN2- Threshold V = 3.8V, V falling 0.72 X V SS2 IN2- I , I V = V = 3.8V Soft Start Discharge Current .4 µA SS _DIS SS2_DIS SS SS2 V , SSRCV Overload Recovery Soft Start Voltage V and V Falling 0.3 0.5 0.7 V SS SS2 V SSRCV2 Gate Driver Disable SS/EN Voltage 0.7 0.9 V Gate Driver Enable SS/EN Voltage .2 .5 V Internal 0.5V Reference Buffer V Output Voltage I = -mA 490 500 50 mV REF REF Load Regulation 0 < I <-5mA 0.05 %/mA REF Notes: () Guaranteed by design. 5 - AVCC Current in UVLO(mA) E/A GM(uW ) Cycle by Cycle OCP Threshols(mV) SS/EN Threshold Voltage(V) AVCC operation Current(mA) COMP SINK/SOURCE Current(uA) Switching Frequency(KHz) SS/EN Threshold Voltage(V) AVCC UVLO(V) VREF(mV) COMP Switching Threshold(V) SS/EN Threshold Voltage(V) SC2443 Typical Characteristics AVCC operation current vs. AVCC current in UVLO vs. UVLO Threshold vs. Temperature Temperature Temperature 4.55 12.9 1.85 12.8 4.54 1.80 12.7 4.53 12.6 1.75 12.5 4.52 1.70 12.4 4.51 12.3 1.65 12.2 4.50 1.60 12.1 4.49 12 1.55 -40 25 85 -40 25 85 -40 25 85 O O O Temperature ( C) Temperature ( C) Temperature ( C) COMP Sink/Source current vs. VREF vs. Temperature E/A GM vs. Temperature Temperature 502.0 20 290 15 280 501.5 SINK 10 270 501.0 5 260 500.5 0 250 500.0 -5 240 SOURCE 499.5 -10 230 499.0 -15 220 -40 25 85 -40 25 85 -40 25 85 O O O Temperature ( C) Temperature ( C) Temperature ( C) Switching Frequency setting vs. COMP switching Threshold vs. Cycle by Cycle OCP threshold vs. Temperature Temperature Temperature 2.35 512 75.0 510 74.5 2.30 508 74.0 2.25 506 73.5 2.20 504 73.0 502 72.5 2.15 500 72.0 2.10 498 71.5 ROSC = 5.KW 2.05 496 71.0 -40 25 85 -40 25 85 -40 25 85 O O O Temperature ( C) Temperature ( C) Temperature ( C) SS/EN Threshold for Overload Hiccup vs. SS/EN Threshold for Gate Driver SS/EN Threshold for Overload Temperature Enable / Disable vs. Temperature Hiccup Recovery vs. Temperature 3.18 1.30 0.58 1.25 3.17 Enable 0.56 1.20 3.16 0.54 1.15 3.15 0.52 1.10 3.14 1.05 0.50 1.00 3.13 0.48 0.95 3.12 Disable 0.46 0.90 3.11 0.44 0.85 3.10 0.80 0.42 -40 25 85 -40 25 85 -40 25 85 O O O Temperature ( C) Temperature ( C) Temperature ( C) 6 SC2443 Typical Application Circuit Performance Circuit Conditions : Single output current share configuration as shown in page 5 Releasing SS/EN pin from GND Soft Start Releasing SS/EN pin from GND VIN VIN 5V/DIV 5V/DIV EN/SS 2V/DIV COMP V/DIV COMP EN/SS V/DIV GDL 2V/DIV EN/SS 5V/DIV 2V/DIV VIN 2V/DIV VOUT VOUT VOUT V/DIV V/DIV V/DIV 0ms/DIV 0ms/DIV 0ms/DIV Gate Wavefroms Shuting down _ VIN ramp down Pulling SS/EN pin to GND VIN VIN 2V/DIV 5V/DIV GDH GDL 0V/DIV EN/SS EN/SS 2V/DIV 2V/DIV GDL GDL 0V/DIV 0V/DIV GDH2 GDL2 VOUT VOUT 0V/DIV V/DIV V/DIV ms/DIV 400us/DIV us/DIV Output Ripple _ IOUT = 40A Transient Response _ 0A ~ 30A OCP Trip _ IOUT = 56A SS/EN GDH 2V/DIV GDH2 0V/DIV VOUT GDH 50mV/DIV 20V/DIV GDL 0V/DIV VOUT 20mV/DIV VOUT 0.5V/DIV 200us/DIV us/DIV 400us/DIV Efficiency (2VIN to VOUT) OCP Recovery to 30A loading EFF (%) 90 80 SS/EN 70 2V/DIV GDH 60 20V/DIV GDL 0V/DIV 50 40 VOUT 0.5V/DIV 30 20ms/DIV IOUT(A) 1 5 10 15 20 25 30 35 40 7 SC2443 Typical Application Circuit Performance Circuit Conditions : Dual independent outputs configuration as shown in page 7 Soft Start (VOUT) Soft Start (VOUT2) Soft Start (Both outputs) SS/EN 2V/DIV VOUT COMP2 0.5V/DIV V/DIV COMP EN2/SS2 EN/SS 2V/DIV 2V/DIV SS2/EN2 VIN VIN 2V/DIV 2V/DIV 2V/DIV VOUT VOUT2 VOUT2 V/DIV 2V/DIV 2V/DIV 20ms/DIV 0ms/DIV 0ms/DIV Output Ripple (VOUT_20A) Gate waveforms (VOUT_2 = 20A) Output Ripple (VOUT2_20A) GDH GDL GDH2 0V/DIV GDH GDL2 GDL 0V/DIV 0V/DIV VOUT2 GDH2 VOUT 50mV/DIV GDL2 50mV/DIV 0V/DIV us/DIV us/DIV us/DIV Transient Response (VOUT _ 2A ~ 7A) Transient Response (VOUT2 _ 2A ~ 7A) OCP Trip (VOUT = 30A) SS/EN 2V/DIV VOUT2 VOUT 50mV/DIV 50mV/DIV GDH GDL 20V/DIV VOUT 0.5V/DIV 200us/DIV 200us/DIV 400us/DIV OCP Trip (VOUT2 = 28A) EFF (%) Combined Efficiency (2VIN to VOUT & 2.5VOUT) 95 90 SS2/EN2 2V/DIV 85 GDH2 20V/DIV GDL2 80 0V/DIV 75 VOUT2 V/DIV 70 400us/DIV 1 5 10 15 20 IOUT(A) 8 SC2443 Pin Descriptions Pin # Pin Name Pin Function  IN- Inverting Input of the Error Amplifier for the Step-down Controller . 2 COMP The Error Amplifier Output for Step-down Controller . Edge-triggered Synchronization Input. When not synchronized, tie this pin to a voltage above .5V 3 SYNC or the ground. An external clock (frequency > frequency set with ROSC) at this pin synchronizes the controllers. 4 AGND Analog Signal Ground Buffered Output of the Internal 0.5V Reference. The non-inverting input of the error amplifier for the 5 REF step-down converter  is internally connected to this pin An external Reference voltage is applied to this pin.The non-inverting input of the error amplifier for 6 REFIN the step-down converter 2 is internally connected to this pin. 7 COMP2 The Error Amplifier Output for Step-down Controller 2. Inverting Input of the Error Amplifier for the Step-down Controller 2. Tie to AVCC for two-phase single 8 IN2- output applications. 9 CS2- The Inverting Input of the Current-sense Amplifier/Comparator for the Controller 2. 0 CS2+ The Non-inverting Input of the Current-sense Amplifier/Comparator for the Controller 2. An external capacitor tied to this pin sets (i) the soft-start time (ii) output overload latch off time for  SS2/EN2 step-down converter 2. Pulling this pin below 0.7V shuts off the gate drivers for the second controller. Leave open for two-phase single output applications. 2 AVCC Power Supply Voltage for the Analog Portion of the Controllers. 3 BST2 Bootstrapped Supply for the High-side Gate Drive 2. 4 GDH2 Gate Drive Output for the High-side N-channel MOSFET of Output 2. 5 GDL2 Gate Drive Output for the Low-side N-channel MOSFET of Output 2. 6 PGND Ground Supply for All the Gate drivers. 7 PVCC Power Supply Voltage for Low-side MOSFET Drivers. 8 GDL Gate Drive Output for the Low-side N-channel MOSFET of Output . 9 GDH Gate Drive Output for the High-side N-channel MOSFET of Output . 20 BST Bootstrapped Supply for the High-side Gate Drive . An external capacitor tied to this pin sets (i) the soft-start time (ii) output overload latch off time for 2 SS/EN buck converter . Pulling this pin below 0.7V shuts off the gate drivers for the first controller. 22 CS+ The Non-inverting Input of the Current-sense Amplifier/Comparator for the Controller . 23 CS- The Inverting Input of the Current-sense Amplifier/Comparator for the Controller  24 ROSC An external resistor connected from this pin to GND sets the oscillator frequency THPAD Solder to the Analog ground plane of the PCB. 9 SC2443 Block Diagram SYNC AVCC 3 CLK2 12 REFERENCE OSCILLATOR ROSC CLK1 UVLO 24 4.3/4.5V BST1 COMP1 20 2 IN1- GDH1 19 1 - R EA1 REF/IN1+ - PWM Q + Non-Overlapping 5 S + PVCC Conduction 17 0.5V Control + GDL1 UVLO - 18 0.75 VREF PGND SLOPE CS1+ COMP 16 OL Soft-Start And 22 + + + CS1- DSBL Overload ISEN 6 - 23 Hiccup SS1/EN1 Control 21 + ILIM+ - 75mV - OCN ILIM- 110mV + COMP2 7 IN2- 8 - EA2 REF /IN2+ IN + 6 + - 0.72 VREF AGND OUT 4 SC2443 Block Diagram (Channel  PWM Control Only) Figure 1. SC2443 Block Diagram 0 SC2443 Applications Information Description The SC2443 is a constant frequency 2-phase current-mode The supply voltages for the high-side gate drivers are step-down PWM switching controller driving all N-channel obtained from two diode-capacitor bootstrap circuits. If MOSFET. The two channels of the controller operate at the bootstrap capacitor is charged from VCC, the high- 80 degrees out-of-phase from each other. Since input side gate drive voltage swing will be from approximately currents are interleaved in a two-phase converter, input 2VCC to the ground. The power dissipated in the high- ripple current is lower and smaller input capacitor can side gate driver is not higher with higher voltage swing be used for filtering. Also, with lower inductor current because the gate-source voltage of the high-side MOSFET 2 and smaller inductor ripple current per phase, overall I R still swing from zero to VCC. The outputs of the low-side losses are reduced. gate drivers swing from VCC to ground. The SC2443 operates in synchronous continuous- The SC2443 has internal ramp-compensation to prevent conduction mode. It can be configured either as two sub-harmonic oscillation when operating above 50% independent step-down controllers producing two duty cycle. There is enough ramp internally for a sensed separate outputs or as a dual-phase single-output voltage ripple between /4 to /3 of the full-scale sensed controller by tying the IN2- pin to VCC. In single output voltage limit of 75mV. The maximum sensed voltage limit operation, the channel one error amplifier controls both is unaffected by the compensating ramp. channels and the channel two error amplifier is disabled. Soft-start and overload hiccup of both channels is Current-Sensing synchronized to channel one. There are two ways to sense the inductor current for current-mode control with the SC2443. Since the peak Frequency Setting and Synchronization inductor current corresponds to 75mV of sensed voltage The internal oscillator of the SC2443 runs at twice the (CS+ - CS-), resistor current sensing can be used at the phase frequency. The free-running frequency of the output without resulting in excessive power dissipation. oscillator can be programmed with an external resistor Although accurate and far easier to lay out than high-side from the ROSC pin to ground. The step-down controllers resistor sensing, a pair of precision sense resistors adds are capable of operating up to  MHz. It is necessary to cost to the converter. consider the operating duty-ratio before deciding the switching frequency. See Applications Information section With proper RC filter, Inductor DCR sensing can also be for more details. used for SC2443 resulting in low cost and without extra power dissipation. When synchronized externally, the applied clock frequency should be twice the desired phase frequency. The Error Amplifiers synchronizing clock frequency should also be between 2 In closed loop operation, the error amplifier output ranges - 2.6 times the set free-running channel frequency. from .V to 3.5V. The upper output operating range of either error amplifier is reserved for positive current- Control Loop sense voltage (CS+ - CS-) and corresponds to positive The SC2443 uses peak current-mode control for fast (sourcing) output current. If the amplifier swings to its transient response, ease of compensation and current lower operating range, the amplifier will still modulate the sharing in single output operation. The low-side MOSFET high-side gate drive duty-ratio. However the peak current- of each channel is turned off at the falling-edge of the sense voltage (hence the peak inductor current) will be phase timing clock. After a brief non-overlapping time limited to a negative value. The error amplifier output interval of 90ns, the high-side MOSFET is turned on. is about 2.2V when the peak sense-voltage is zero. The The phase inductor current ramps up. When the sensed built-in offset in the current sense amplifier together with inductor current reaches the threshold determined by synchronous continuous-conduction mode of operation the error amplifier output and compensation ramp, the allows the SC2443 to regulate the output irrespective of high-side MOSFET is turned off. After a non-overlapping the direction of the load current. conduction time of 90ns, the low-side MOSFET is turned on.  SC2443 Applications Information (continued) current reaching its current limit and the instant the The non-inverting input of the first feedback amplifier is converter shuts down. This is due to cycle skipping(a tied to the internal 0.5V voltage reference. Both the non- consequence of inductor current sense) reduces the inverting and the inverting inputs of the second error actual operating frequency. amplifier are brought out as device pins so that the output of the second converter can be made to track the output The SS/EN pin can also be used as the enable input for that of the first channel. For example in DDR applications, channel. Both the high-side and the low-side MOSFETs Channel  can be used to generate VDDQ (2.5V) from will be turned off if the SS/EN pin is pulled below 0.7V. the input (5V or 2V) and channel 2 is used to produce a tracking VTT (.25V) with VDDQ being its input. Operating Frequency (fs) The switching frequency in the SC2443 is user- Current-Limit programmable. The advantages of using constant The maximum current sense voltage of +75mV is the frequency operation are simple passive component cycle-by-cycle peak current limit when the load is selection and ease of feedback compensation. Before drawing current from the converter. There is no cycle-by- setting the operating frequency, the following trade-offs cycle current limiting when the inductor current flows in should be considered. the negative direction. However once the valley of the ) Passive component size current sense voltage exceeds -0mV, the corresponding 2) Circuitry efficiency channel will undergo shutdown and restart (hiccup). 3) EMI condition 4) Minimum switch on time and 5) Maximum duty ratio Soft-Start and Overload Protection The undervoltage lockout circuit discharges the SS/EN For a given output power, the sizes of the passive capacitors. After VCC rises above 4.5V, the SS/EN capacitors components are inversely proportional to the switching are slowly charged by internal 2mA current source. With frequency, whereas MOSFET and Diodes switching losses internal PNP transistors, the SS/EN voltages clamp the error are proportional to the operating frequency. Other amplifier outputs. When the error amplifier output rises issues such as heat dissipation, packaging and the cost to 2.2V, the high-side MOSFET starts to switch. As the SS/ issues are also to be considered. The frequency bands EN capacitor continues to be charged, the COMP voltage for signal transmission should be avoided because of EM follows. The converter gradually delivers increasing power interference. to the output. The inductor current follows the COMP voltage envelope until the output goes into regulation. The SS/EN clamp on COMP is then released. Minimum Switch On Time Consideration In the SC2443 the falling edge of the clock turns on the After the SS/EN capacitor is charged above 3.2V (high top MOSFET. The inductor current and the sensed voltage enough for the error amplifier to provide full load current), ramp up. After the sensed voltage crosses a threshold the overload detection circuit is activated. If the output determined by the error amplifier output, the top MOSFET voltage falls below 70% of its set value or the valley is turned off. The propagation delay time from the turn- current-sense voltage exceeds -0mV, an overload latch on of the controlling FET to its turn-off is the minimum will be set and both the top and the bottom MOSFETs will switch on time. The SC2443 has a minimum on time of be turned off. The SS/EN capacitor is slowly discharged about 50ns at room temperature. This is the shortest on with an internal .4mA current sink. The overload latch interval of the controlling FET. The controller either does is reset when the SS/EN capacitor is discharged below not turn on the top MOSFET at all or turns it on for at least 0.5V. The SS/EN capacitor is then recharged with the 2uA 50ns. current source and the converter undergoes soft-start. For a synchronous step-down converter, the operating If overload persists, the SC2443 will undergo repetitive duty cycle is . So the required on time for the VO /VIN shutdown and restart. top MOSFET is VO /(VIN×F) . If the frequency is set S such that the required pulse width is less than 50ns, If the output is short-circuited, the inductor current will then the converter will start skipping cycles. Due to not increase indefinitely between the time the inductor minimum on time limitation, simultaneously operating at 2 SC2443 Applications Information (continued) very high switching frequency and very short duty cycle is not practical. If the voltage conversion ratio VO /VIN PC Board Layout Issues and hence the required duty cycle is higher, the switching Circuit board layout is very important for the proper frequency can be increased to reduce the sizes of passive operation of high frequency switching power converters. components. A power ground plane is required to reduce ground There will not be enough modulation headroom if the bounces. The following are suggested for proper layout: on time is simply made equal to the minimum on time of the SC2443. For ease of control, we recommend the Power Stage required pulse width to be at least .5 times the minimum ) Separate the power ground from the signal ground. In on time. the SC2443, the power ground PGND should be tied to the source terminal of lower MOSFETs. The signal ground Setting the Switching Frequency AGND should be tied to the negative terminal of the The switching frequency is set with an external resistor output capacitor. connected from Pin 24 to ground. The set frequency is inversely proportional to the resistor value (Figure 2). 2) Minimize the size of high pulse current loop. Keep the top MOSFET, bottom MOSFET and the input capacitors Figure 2. Free running frequency vs. ROSC. within a small area with short and wide traces. In addition to the aluminum energy storage capacitors, add multi- layer ceramic (MLC) capacitors from the input to the 800 power ground to improve high frequency bypass. 700 600 3) Reduce high frequency voltage ringing. Widen and 500 shorten the drain and source traces of the MOSFET to 400 reduce stray inductances. Add a small RC snubber if necessary to reduce the high frequency ringing at the 300 phase node. Sometimes slowing down the gate drive 200 signal also helps in reducing the high frequency ringing 100 at the phase node. 0 0 50 100 150 200 250 4) Shorten the gate driver path. Integrity of the gate drive Rosc (k Ohm) (voltage level, leading and falling edges) is important for circuit operation and efficiency. Short and wide gate drive traces reduce trace inductances. Bond wire inductance is about 2~3nH. If the length of the PCB trace from the gate Setting the Output Voltage driver to the MOSFET gate is  inch, the trace inductance The non-inverting input of the channel-one error amplifier will be about 25nH. If the gate drive current is 2A with is internally tied the 0.5V voltage reference output (Pin 5). 0ns rise and falling times, the voltage drops across The non-inverting input of the channel-two error amplifier the bond wire and the PCB trace will be 0.6V and 5V is brought out as a device pin (Pin 6) to which the user can respectively. This may slow down the switching transient connect Pin 5 or an external voltage reference. A simple of the MOSFET. These inductances may also ring with the voltage divider (Ro at top and Ro2 at bottom) sets the gate capacitance. converter output voltage. The voltage feedback gain h=0.5/Vo is related to the divider resistors value as 5) Put the decoupling capacitor for the gate drive power h R = R supplies (BST and PVCC) close to the IC and power o2 o1. 1- h ground. Control Section 6) The frequency-setting resistor Rosc should be placed close to Pin 3. Trace length from this resistor to the analog 3 fs (kHz) SC2443 Applications Information (continued) ground should be minimized. 7) Solder the bias decoupling capacitor right across the AVCC and analog ground AGND. 8) Place the inductor DCR sense components away from the power circuit and close to the corresponding CS+ and CS- pins. Use X7R type ceramic capacitor for the DCR sense capacitor because of their temperature stability. 9) Use an isolated local ground plane underneath the controller and tie it to the negative side of output capacitor bank. 0) Comp pin is sensitive to noise. Place compensation network components away from noise signal (i.e. gate driver signals, phase node) and close to corresponding Comp pin . 4 10uF/6.3V N.P. 1500uF/6.3V/FL 1500uF/6.3V/FL 1500uF/6.3V/FL 10uF/6.3V 270uF/16V/OSCON 270uF/16V/OSCON 270uF/16V/OSCON IPD06N03LA IPD06N03LA 10uF/16V 10uF/16V 12VIN C2 C3 C1 D1 1N4148 Q1 IPD09N03LA R1 0R L1 1.5uH/1.8mR C5 R2 100nF 10K C4 1uF CS1- CS1+ R3 C6 22pF R4 C7 Q2 Q3 1R R6 N.P. R5 IPD06N03LA 10R 22nF CS1+ 124K R7 0R C8 CS1- R8 U1 2.2nF 560R 1VOUT/40A IN1- 1 18 IN1- GDL1 12VIN R9 47K 2 17 R10 2R2 C14 C15 C16 C17 C18 C19 COMP1 PVCC C11 C9 D2 C10 C12 C13 3 16 1uF 1N4148 SYNC PGND Q4 330pF N.P SC2443 4 15 R11 0R IPD09N03LA L2 1.5uH/1.8mR AGND GDL2 C21 R12 10K 100nF 5 14 C20 1uF REF GDH2 R13 C22 R15 6 13 1.05K REFIN BST2 R14 Q5 Q6 1R 22pF R16 N.P. IPD06N03LA 10R IN1- R17 0R C24 C23 2.2nF R19 R20 100nF R18 0R 560R 1K R21 10R 12VIN C25 1uF SC2443 Evaluation Application Circuit _ Single Output, Current share configuration 7 24 COMP2 ROSC 8 23 IN2- CS1- 9 22 CS2- CS1+ 10 21 CS2+ SS1/EN1 11 20 SS2/EN2 BST1 12 19 AVCC GDH1 5 SC2443 Evaluation Board Bill of Materials Single Output Current Share Configuration Item Reference Quantity Description Package Part Vendor  C,C0 2 6V X5R ceramic capacitor 206 0uF Murata 2 C2,C3,C 3 6V Aluminum solid capacitor _SEPC series 8 X 9mm 270uF Sanyo 3 C4,C9,C20,C25 4 6V X5R ceramic capacitor 0603 uF Murata 4 C5,C2,C23 3 6V X7R ceramic capacitor 0603 00nF Panasonic 5 C6,C22 2 25V X7R ceramic capacitor 0603 22pF Panasonic 16V X7R 0603 6 C7  ceramic capacitor 22nF Panasonic 7 C8,C24 2 25V X7R ceramic capacitor 0603 2.2nF Panasonic 8 C2  25V X7R ceramic capacitor 0603 330pF Panasonic 9 C4,C9 2 6.3V X7R ceramic capacitor 206 0uF Murata 0 C5,C6,C7 3 6.3V Aluminum capacitor _ FL series 8 X .5mm 000uF Panasonic  D,D2 2 Small signal diode SMD N448 Any 2.5 X 2.5 X 2 L,L2 2 SMD inductor .5uH/.8mR TRIO 0mm 3 Q,Q4 2 30V N Channel MOSFET D-pack IPD09N03LA Infineon 4 Q2,Q3,Q5,Q6 4 30V N Channel MOSFET D-pack IPD06N03LA Infineon R,R7,R, 5 5 5% SMD resistor 0603 0R Any R7,R8 6 R2,R2 2 5% SMD resistor 0603 0K Any 7 R3,R3 2 5% SMD resistor 0603 R Any 8 R5  % SMD resistor 0603 24K Any 9 R6,R6.R2 3 % SMD resistor 0603 0R Any 20 R8,R9 2 % SMD resistor 0603 560R Any 2 R9  5% SMD resistor 0603 47K Any 22 R0  5% SMD resistor 0603 2R2 Any 23 R5  % SMD resistor 0603 .05K Any 24 R20  % SMD resistor 0603 K Any 25 U  Dual phase Sync. step down controller MLPQ-24 SC2443 SEMTECH 6 10uF/6.3V 22uF/10V/X7R 1800uF/6.3V/FL 2200uF/6.3V/FL 1800uF/6.3V/FL 2200uF/6.3V/FL 10uF/6.3V 22uF/10V/X7R N.P. 1500uF/16V/FL 1500uF/16V/FL 10uF/16V 10uF/16V IPD09N03LA IPD09N03LA 22nF 22nF N.P. 12VIN C3 C1 C2 D1 1N4148 Q1 R1 L1 0R 2.2uH/2mR C4 1VOUT/20A 1uF R2 C5 15K 100nF CS1- CS1+ R3 Q3 1R C8 C9 C10 C11 R5 C7 N.P. 1.05K R8 Q2 R4 C6 27pF R6 R7 0R IN1- IPD06N03LA N.P. 124K 0R CS1+ C12 CS1- 2.2nF U1 R9 R10 1N1- N.P. 1K 1 18 SYNC IN1- GDL1 R12 2R2 2 17 12VIN COMP1 PVCC R11 C13 D2 C14 C15 47K C17 3 16 1uF 1N4148 Q4 SYNC PGND N.P. R25 L2 C16 SC2443 4 15 2.2uH/2mR 470pF 0R AGND GDL2 R13 2.5VOUT/20A C19 R14 0R 5 14 100nF 20K REF GDH2 C18 1uF Q6 6 13 R15 C21 C22 C23 C24 R17 REFIN BST2 N.P. 1R 4.12K C20 N.P. R16 R18 N.P. 0R C25 R19 R20 2.2nF 0R Q5 R21 R22 R23 IPD06N03LA N.P. 1K 10R 100K C29 12VIN C26 C28 C27 100nF 470pF C30 1uF R24 0R SC2443 Evaluation Application Circuit_ Dual Independant Outputs 7 7 24 COMP2 ROSC 8 23 IN2- CS1- 9 22 CS2- CS1+ 10 21 CS2+ SS1/EN1 11 20 SS2/EN2 BST1 12 19 AVCC GDH1 SC2443 Evaluation Board Bill of Materials Dual Independent Output Configuration Item Reference Quantity Description Package Part Vendor  C,C4 2 6V X5R ceramic capacitor 206 0uF Murata 2 C2,C5 2 6V Aluminum capacitor _FL series 0 X 20mm 500uF Panasonic C4,C3,C8, 3 4 6V X5R ceramic capacitor 0603 uF Murata C30 4 C5,C9,C26 3 6V X7R ceramic capacitor 0603 00nF Panasonic 5 C6  25V X7R ceramic capacitor 0603 27pF Panasonic 0603 16V X7R 6 C7,C29 2 ceramic capacitor 22nF Panasonic 7 C8,C 2 6.3V X7R ceramic capacitor 206 0uF Murata 8 C9,C0 2 6.3V Aluminum capacitor _ FL series 0 X 6mm 800uF Panasonic 9 C2,C25 2 25V X7R ceramic capacitor 0603 2.2nF Panasonic 0 C6,C27 2 25V X7R ceramic capacitor 0603 470pF Panasonic  C2,C24 2 0V X7R ceramic capacitor 206 0uF Murata 2 C22,C23 2 6.3V Aluminum capacitor _ FL series 0 X 20mm 2200uF Panasonic 3 D,D2 2 Small signal diode SMD N448 Any 4 L,L2 2 Through hole inductor 2.2uH/2mR Any 5 Q,Q4 2 30V N Channel MOSFET D-pack IPD09N03LA Infineon 6 Q2,Q5 2 30V N Channel MOSFET D-pack IPD06N03LA Infineon R,R7,R,R3, 7 R8,R9,R24 8 5% SMD resistor 0603 0R Any R25 8 R2  5% SMD resistor 0603 5K Any 9 R3,R5 2 5% SMD resistor 0603 R Any 20 R5  % SMD resistor 0603 .05K Any 2 R6  % SMD resistor 0603 24K Any 22 R0,R22 2 % SMD resistor 0603 K Any 23 R  5% SMD resistor 0603 47K Any 24 R2  5% SMD resistor 0603 2R2 Any 25 R4  5% SMD resistor 0603 20K Any 26 R7  % SMD resistor 0603 4.2K Any 27 R20  5% SMD resistor 0603 00K Any 28 R23  5% SMD resistor 0603 0R Any 29 U  Dual phase Sync. step down controller MLPQ-24 SC2443 SEMTECH 8 5 4 3 2 1 D D 12VIN Q1 C1 C2 D1 1N4148 R1 L1 0R 1.9uH/3.9mR C4 1.5VOUT R2 C5 1uF 100nF/X7R 4.87K R8 CS1- CS1+ R3 0R 1R C8 C9 C10 C11 R5 C7 2.05K R4 C6 27pF R6 R7 IN1- N.P. 102K 10R CS1+ FDS6982 C12 CS1- 2.2nF U1 R9 R10 1N1- 604R 1K 1 18 C SYNC C IN1- GDL1 R12 12VIN 2R2 2 17 COMP1 PVCC Q2 R11 C13 D2 C14 C15 47K C17 1uF 1N4148 3 16 SYNC PGND N.P. R25 L2 C16 SC2443 1.9uH/3.9mR 0R 4 15 470pF AGND GDL2 R13 1.8VOUT R14 C19 0R 100nF/X7R 5 14 4.87K REF GDH2 C18 1uF R15 C21 C22 C23 C24 R17 6 13 REFIN BST2 1R 2.61K C20 18pF R16 R18 N.P. 10R FDS6982 C25 R19 R20 2.2nF 0R R21 R22 R23 604R 1K 10R 47K C29 VIN C26 C28 B B C27 100nF 470pF C30 1uF R24 0R A A Title SC2443 Dual independant Outputs Size Document Number Rev A Date: Tuesday, December 11, 2007 Sheet 1 of 1 5 4 3 2 1 SC2443 Evaluation Application Circuit_ Dual Independant Outputs (Lower power application) 7 24 COMP2 ROSC 8 23 IN2- CS1- 9 22 CS2- CS1+ 10 21 CS2+ SS1/EN1 11 20 SS2/EN2 BST1 12 19 AVCC GDH1 9 N.P N.P N.P N.P 1000uF/6.3V/FL 1000uF/6.3V/FL 10uF/6.3V 10uF/6.3V/X7R 680uF/16V/FL 680uF/16V/FL 10uF/16V 10uF/16V 22nF 22nF N.P. SC2443 Evaluation Board Bill of Materials Dual Independent Output Configuration Item Reference Quantity Description Package Part Vendor  C,C4 2 6V X5R ceramic capacitor 206 0uF Murata 2 C2,C5 2 6V Aluminum capacitor _FL series 0 X 2.5mm 680uF Panasonic C4,C3,C8, 3 4 6V X5R ceramic capacitor 0603 uF Murata C30 4 C5,C9,C26 3 6V X7R ceramic capacitor 0603 00nF Panasonic 5 C6  25V X7R ceramic capacitor 0603 27pF Panasonic 0603 16V X7R 6 C7,C29 2 ceramic capacitor 22nF Panasonic 7 C8,C2 2 6.3V X7R ceramic capacitor 206 0uF Murata 8 C9,C22 2 6.3V Aluminum capacitor _ FL series 0 X 2.5mm 000uF Panasonic 9 C2,C25 2 25V X7R ceramic capacitor 0603 2.2nF Panasonic 0 C6,C27 2 25V X7R ceramic capacitor 0603 470pF Panasonic  C20  25V X7R ceramic capacitor 0603 8pF Murata 2 D,D2 2 Small signal diode SMD N448 Any 3 L,L2 2 Through hole inductor .9uH/3.9mR Any 4 Q,Q2 2 30V N Channel MOSFET SO-8 FDS6982 Fairchild R,R8,R3, 5 6 5% SMD resistor 0603 0R Any R9,R24,R25 6 R2,R4 2 5% SMD resistor 0603 4.87K Any 7 R3,R5 2 5% SMD resistor 0603 R Any 8 R5  % SMD resistor 0603 2.05K Any 9 R6  % SMD resistor 0603 02K Any 20 R7,R8,R23 3 5% SMD resistor 0603 0R Any 2 R9,R2 2 5% SMD resistor 0603 604R Any 22 R0,R22 2 % SMD resistor 0603 K Any 23 R,R20 2 5% SMD resistor 0603 47K Any 24 R2  5% SMD resistor 0603 2R2 Any 25 R7  % SMD resistor 0603 2.6K Any 26 U  Dual phase Sync. step down controller MLPQ-24 SC2443 SEMTECH 20 SC2443 Outline Drawing - MLPQ-24 A D B DIMENSIONS INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX A .031 .035 .039 0.80 0.90 1.00 A1 .000 .001 .002 0.00 0.02 0.05 - A2 - (.008) - - (0.20) PIN 1 b .007 0.25 0.30 .010 .012 0.18 E INDICATOR D .152 .157 .163 3.85 4.00 4.15 (LASER MARK) D1 .100 .106 .110 2.55 2.70 2.80 E .152 .157 .163 3.85 4.00 4.15 E1 .100 .106 .110 2.55 2.70 2.80 e .020 BSC 0.50 BSC L .012 .016 .020 0.30 0.40 0.50 N 24 24 aaa .004 0.10 A2 bbb .004 0.10 A SEATING PLANE aaa C A1 C D1 LxN E/2 E1 2 1 N bxN bbb C A B e D/2 NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. © Semtech, Inc. All Rights Reserved. An ISO-registered company. Semtech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Semtech product. No circuit patent licenses are implied. Semtech reserves the right to change the circuitry and specifications without notice at any time. Trademarks and Copyrights belong to their respective holders. © 2007 Semtech Corporation 2 SC2443 Land Pattern - MLPQ-24 K DIMENSIONS DIM INCHES MILLIMETERS (.156) (3.95) C 3.10 G .122 H .106 2.70 G Z (C) H K .106 2.70 P .020 0.50 X .010 0.25 Y .033 0.85 Z .189 4.80 X P NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 2. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. Contact Information Semtech Cor poration Power Management Products Division 200 Flynn Road, Camarillo, CA 9302 Phone: (805) 498-2 Fax: (805) 498-3804 www.semtech.com 22