SEMTECH SC4521

SC4521 3A Step-Down Switching Regulator with Programmable Soft Start POWER MANAGEMENT Description Features The SC4521 is a current mode switching regulator with ‹ Wide operating voltage range: 4.4V to 24V an integrated switch, operating at 600kHz with ‹ Integrated 3 Amp switch programmable soft start and enable functions. The ‹ 600kHz frequency of operation integrated switch allows for cost effective low power ‹ Programmable soft start funchion solutions (peak switch current 3 amps). High frequency ‹ Current mode control operation allows for very small passive components. ‹ Precision enable threshold Current mode operation allows for fast dynamic response ‹ SO-8 EDP Lead-free package, fully WEEE and RoHS and instantaneous duty cycle adjustment as the input compliant varies (ideal for CPE applications where the input is a wall plug power). Applications ‹ XDSL modems The low shutdown current makes it ideal for portable ‹ CPE equipment applications where battery life is important. ‹ DC-DC point of load applications The SC4521 is an 600kHz switching regulator with a low ‹ Portable equipment pin count. ‹ Digtial consumer electronics The SC4521 allows customers to use large capacitive loads because its programmable soft start limits the dv/ dt of the output at start up. Typical Application Circuit D1 D1 C1 C1 1 1 L1 L1 BST BST 2 2 3 3 V V IN IN SW SW V V IN IN OUT OUT 5 5 6 6 Enable Enable EN EN SC4521 SC4521 FB FB R1 R1 8 8 7 7 C2 C2 C3 C3 SS SS COMP COMP D2 D2 GND GND 4 4 R2 R2 C6 C6 C4 C4 R3 R3 Revision: October 5, 2007 1 www.semtech.com SC4521 POWER MANAGEMENT Absolute Maximum Ratings Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability. Pl arameter Ss ymbo Ls imit Unit IV nput Supply Voltage -V 0.3 to +28 IN Boost Pin Above V (V - V)61V SW BST SW BV oost Pin Voltage -V 0.3 to +32 BST EV N Pin Voltage -V 0.3 to +24 EN FV B Pin Voltage -V 0.3 to +6 FB FI B Pin Current 1A m FB SV S Pin Voltage +V 3 SS (1) Thermal Impedance Junction to Ambient 3W 6.5 °C/ θ JA Me aximumJT unction Temperatur 1C 50 ° J ST torage Temperature Range -C 65 to +150 ° STG LT ead Temperature (Soldering) 10 sec 3C 00 ° LEAD ED SD Rating (Human Body Model) E2 S kV Note: (1) ThetaJA is calculated from a package in still air, mounted to 3" x 4.5", 4 layer FR4 PCB with thermal vias under exposed pad per JESD51 standards. Electrical Characteristics Unless specified: V = 12V, V = 0.8V, V = V + 5V, EN = tied to V , SW = open. IN COMP BST IN IN T = T = -40°C to 125°C. A J Pl arameter Ss ymbo Cn ondition Mp i Tx yMs a Unit OV perating Input Voltage 2V 4 IN MI aximum Switch Current Limit T=5 25°C, D = 50% 35 . 5A . SW A Of scillator Frequency 50 0060 07z 0 kH OSC SV witch On Voltage Drop I=0 3A 2V 2 m D(SW) SW VRV ising Undervoltage Lockout T=9 0°C to 85°C 34 . 4V . IN UVLO J VUV VLO Hysteresis 6V 0 m IN HYST VSI upply Current V=3 1V 5A .5 m IN Q FB SI tandby Current V=0 0V 2A 5 µ Q(OFF) EN Thermal Shutdown Trip Point 1C 55 ° Thermal Shutdown Hysteresis 1C 0 °  2007 Semtech Corp. 2 www.semtech.com SC4521 POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: V = 12V, V = 0.8V, V = V + 5V, EN = tied to V , SW = open. IN COMP BST IN IN T = T = -40°C to 125°C. A J Pl arameter Ss ymbo Cn ondition Mp i Tx y Ms a Unit FI B Input Current -1 0.25 -A µ FB FV eedback Voltage 08 .78406 . 0V .81 FB (1) Feedback Voltage Line 4.4V < V < 24V +V 3 mV/ IN Regulation (2) FB to V Voltage Gain 0.9V ≤ V ≤20 .0V 10 53V 5 V/ COMP COMP FB to V Δ I = ± 10µA 50 0080 51o 30 µMh COMP COMP (2) Transconductance VPV in Source Current =0 0.6V 701A 1 µ COMP FB VPV in Sink Current =0 1.0V -0 7 -A 11 µ COMP FB V Pin to Switch Current V=3 1.25V 4V . A/ COMP COMP Transconductance V Pin Maximum Switching D6 uty cycle = 0% 0V . COMP Threshold VOV CP Threshold r2 ising V COMP COMP VHV iccup Retry Threshold f5 alling 0V .2 COMP COMP MD aximum Switch Duty Cycle V = 1.2V, I=5 400mA8% MAX COMP SW Minimum Boost Voltage Above 2V .7 (2) Switch BI oost Current =0 1A 151A m SW I=0 3A 35 4 SW EV nable Input Threshold Voltage 17 .115 .2 1V . ETH EI nable Output Bias CurrentE8 N = 50mV below threshold µA EOL IE0 N = 50mV below threshold 1A µ EOH (3) Soft Start Charging Current I V=6 0 1A µ SS SS SI oft Start Discharging Current -A 2 m SS Notes: (1) The required minimum input voltage for a regulated output depends on the output voltage and load condition. (2) Guaranteed by design. (3) See Application Information.  2007 Semtech Corp. 3 www.semtech.com SC4521 POWER MANAGEMENT Pin Configurations Ordering Information (1)(2) Part Number Package TOP VIEW SP C4521SETRT SOIC-8L-ED SD C4521EVB EVALUATION BOAR BST 1 8 SS Notes: IN 2 7 COMP (1) Only available in tape and reel packaging. A reel contains 2500 devices. SW 3 6 FB GND 4 5 EN (2) Lead free product. This product is WEEE and RoHS compliant. (SOIC-8L-EDP) Pin Descriptions Pe in #Pn in Nam Pin Functio 1T BS This pin provides power to the internal NPN switch. The minimum turn on voltage for this switch is 2.7V. 2N I Pin IN delivers all power required by control and power circuitry. This pin sees high di/dt during switching. A decoupling capacitor should be attached to this pin as close as possible. 3W S Pin SW is the emitter of the internal switch. The external freewheeling diode should be connected as close as possible to this pin. 4D GN All voltages are measured with respect to this pin. The decoupling capacitor and the freewheeling diode should be connected to GND as short as possible. 5N E This is the chip enable input. The regulator is switched on if EN is high, and it is off if EN is low. The regulator is in standby mode when EN is low, and the input supply current is reduced to a few microamperes. 6BF. Feedback input for adjustable output controllers 7P COM This is the output of the internal error amplifier and input of the peak current comparator. A compensation network is connected to this pin to achieve the specified performance. 8S S Soft start pin. An external capacitor connected from this pin to GND sets the soft start time. -L THERMA Pad for heatsinking purposes. Connect to ground plane using multiple vias. Not connected PAD internally.  2007 Semtech Corp. 4 www.semtech.com SC4521 POWER MANAGEMENT Block Diagram + + IN IN + + Is Is IISEN SEN + + 40 40m m SLOPE SLOPE COM COMP P BS BST T + + PW PWM M S S FB FB - - Q Q PO POW WE ER R EA EA R R T TR RAN ANSI SIST STOR OR SW SW Is Is UV UVL LO O RE REF FE ER RE ENCE NCE EN EN 1. 1.6V IN 6V INT TE ER RN NA AL L S SU UP PP PL LY Y GND GND OL OL HI HICC CCUP UP SLOPE SLOPE SS SS FB FB SLOPE SLOPE C COM OMP P OSC OSCIIL LL LAT ATOR OR FR FRE EQ QU UE ENC NCY Y CL CLK K Typical Characteristic - OCP Limit SC4519H OCP Limit vs Duty Cycle 7 6.5 6 5.5 5 ILIM @-40C 4.5 ILIM @25C ILIM @125C 4 3.5 3 2.5 2 0 2040 6080 100 Duty Cycle (%)  2007 Semtech Corp. 5 www.semtech.com Current Limit (A) SC4521 POWER MANAGEMENT Application Information The SC4521 is a current mode buck converter regulator. about 2V. When an OCP fault is detected, the switch is The SC4521 uses two feedback loops that control the turned off and the external COMP capacitor is gradually duty cycle of the internal power switch. The error amplifier discharged at the rate of dv/dt=3µA/Ccomp. Ccomp is functions like that of the voltage mode converter. The the total capacitance value attached to COMP. At the output of the error amplifier works as a switch current same time, the soft start cap C is quickly discharged. SS reference. This technique effectively removes one of the Once the COMP voltage has fallen below 250mV, the double poles in the voltage mode system. With this, it is part enters a normal startup cycle. In the case of much simpler to compensate a current mode converter sustained overcurrent or dead-short, the part will to have better performance. continually cycle through the retry sequence as described above. Soft Start Enable Internally, connected to the SS pin is a 100K pull-up resistor from an internal 1.6V regulator and the collector Pulling and holding the EN pin below 0.4V activates the of an NPN pull-down transistor from SS to GND. The NPN shut down mode of the SC4521 which reduces the input transistor is “on” when the Enable pin is low or when a supply current to 250µA. During the shut down mode, fault is detected (Input UVLO, Over-Current, or Over the switch is turned off. The SC4521 is turned on if the Temp). When the SC4521 is disabled or when a fault is EN pin is pulled high. detected, the NPN transistor pulls the SS pin low. The SS charging time is controlled by the internal 100k Oscillator resistor and external soft-start cap. This is a closed-loop soft-start which effectively “ramps the reference”. The Its internal free running oscillator sets the PWM frequency SS process completes when the SS pin voltage is at 600kHz for the SC4521 without any external exceeds the internal reference voltage, 0.8V. The SS pin components to program the frequency. continues to charge up to 1.6V, well above the reference voltage to ensure it does not interfere with normal UVLO operation. The governing SS equation is: T = 69000 • C When the EN pin is pulled and held above 1.8V, the voltage SS SS on Pin IN determines the operation of the SC4521. As For example, a 22nF SS cap would give a SS time of VIN increases during power up, the internal circuit senses approximately 1.5mS. VIN and keeps the power transistor off until VIN reaches 4.4V. However, when VI is higher than about 13V, the SC4521 requires a pull-up resistor from the SS pin to VI for normal Load Current operation. The softstart time can be estimated as: 0.8 The peak current I in the switch is internally limited. T = R ⋅ C ⋅ [−Ln(1 − )] SS SS SS PEAK V I For a specific application, the allowed load current I OMAX Where: will change if the input voltage drifts away from the original Rss = pull-up resistance from SS pin to VI, design as given for continuous current mode: Css = capacitance from SS pin to GND, and V ⋅(1− D) O VI = input voltage. I = 3 − OMAX 2 ⋅L ⋅ f s Where: Overcurrent Protection fs = switching frequency, Vo = output voltage and The current sense amplifier in the SC4521 monitors the D = duty ratio, VO/VI switch current during each cycle. Overcurrent protection VI = input voltage. (OCP) is triggered when the current limit exceeds the upper limit of 3A, detected by a voltage on COMP greater than  2007 Semtech Corp. 6 www.semtech.com SC4521 POWER MANAGEMENT Application Information (Cont.) Figure 2 shows the theoretical maximum load current V ⋅ (V − V ) O I O L = for the specific cases. In a real application, however, the V ⋅ f ⋅δ ⋅ I I s OMAX allowed maximum load current also depends on the layout Where: and the air cooling condition. Therefore, the maximum fs = switching frequency, load current may need to be degraded according to the δ = ratio of the peak to peak inductor current to the thermal situation of the application. output load current and V = output voltage. O The peak to peak inductor current is: Maximum Load Current vs Input Voltage I =δ • I p−p OMAX L=10uH After the required inductor value is selected, the proper selection of the core material is based on the peak 2.900 2.880 inductor current and efficiency specifications. The core 2.860 must be able to handle the peak inductor current I 2.840 PEAK Vo=2.5V 2.820 without saturation and produce low core loss during the 2.800 Vo=3.3V high frequency operation. 2.780 Vo=5V 2.760 I 2.740 p−p I = I + PEAK OMAX 2.720 2 2.700 The power loss for the inductor includes its core loss and 46 8 10 12 14 16 18 copper loss. If possible, the winding resistance should Vi (V) be minimized to reduce inductor’s copper loss. The core must be able to handle the peak inductor current I PEAK without saturation and produce low core loss during the Figure 2. Theoretical maximum load current curves high frequency operation. The core loss can be found in the manufacturer’s datasheet. The inductor’s copper loss Inductor Selection can be estimated as follows: 2 The factors for selecting the inductor include its cost, P = I ⋅ R LRMS COPPER WINDING efficiency, size and EMI. For a typical SC4521 application, Where: the inductor selection is mainly based on its value, I is the RMS current in the inductor. This current can LRMS saturation current and DC resistance. Increasing the be calculated as follows: inductor value will decrease the ripple level of the output 1 2 voltage while the output transient response will be I = I ⋅ 1+ ⋅δ LRMS OMAX 12 degraded. Low value inductors offer small size and fast transient responses while they allow large ripple currents, Output Capacitor Selection poor efficiencies and require more output capacitance for low output ripple. The inductor should be able to Basically there are two major factors to consider in handle the peak current without saturating and its copper selecting the type and quantity of the output capacitors. resistance in the winding should be as low as possible to The first one is the required ESR (Equivalent Series minimize its resistive power loss. A good trade-off among Resistance) which should be low enough to reduce the its size, loss and cost is to set the inductor ripple current output voltage deviation during load changes. The second to be within 15% to 30% of the maximum output current. one is the required capacitance, which should be high enough to hold up the output voltage. Before the SC4521 The inductor value can be determined according to its regulates the inductor current to a new value during a operating point under its continuous mode and the switching frequency as follows:  2007 Semtech Corp. 7 www.semtech.com Iomax (A) SC4521 POWER MANAGEMENT Application Information (Cont.) load transient, the output capacitor delivers all the 1 T = ⋅ D W max additional current needed by the load. The ESR and ESL f s of the output capacitor, the loop parasitic inductance Where: between the output capacitor and the load combined f = the switching frequency and s with inductor ripple current are all major contributors to Dmax = maximum duty ratio, 0.85 for the SC4521. the output voltage ripple. Surface mount ceramic capacitors are recommended. The required minimum capacitance for the boost capacitor will be: Input Capacitor Selection I B T C = ⋅ boost W The input capacitor selection is based on its ripple current V D level, required capacitance and voltage rating. This capacitor must be able to provide the ripple current Where: drawn by the converter. For the continuous conduction I = the boost current and B mode, the RMS value of the input capacitor current V = discharge ripple voltage. D I can be calculated from: CIN(RMS) With f = 600kHz, V = 0.5V and I = 0.045A, the required V ⋅ (V − V ) O I O s D B I = I ⋅ CIN OMAX (RMS) 2 minimum capacitance for the boost capacitor is: V I I 1 0.045 1 This current gives the capacitor’s power loss through its B C = ⋅ ⋅D = ⋅ ⋅0.85 = 128nF boost max R as follows: V f 0.5 600k CIN(ESR) D s 2 The internal driver of the switch requires a minimum 2.7V P = I • R CIN CIN (RMS) CIN(ESR) to fully turn on that switch to reduce its conduction loss. The input ripple voltage mainly depends on the input If the output voltage is less than 2.7V, the boost capacitor capacitor’s ESR and its capacitance for a given load, input can be connected to either the input side or an voltage and output voltage. Assuming that the input independent supply with a decoupling capacitor. But the current of the converter is constant, the required input Pin BST should not see a voltage higher than its maximum capacitance for a given voltage ripple can be calculated rating. by: D ⋅ (1 − D) Freewheeling Diode Selection C = I ⋅ IN OMAX fs ⋅ (ΔV − I ⋅ R ) I OMAX CIN (ESR) Where: This diode conducts during the switch’s off-time. The diode ΔV = the given input voltage ripple. should have enough current capability for full load and I short circuit conditions without any thermal concerns. Because the input capacitor is exposed to the large surge Its maximum repetitive reverse block voltage has to be current, attention is needed for the input capacitor. If higher than the input voltage of the SC4521. A low tantalum capacitors are used at the input side of the forward conduction drop is also required to increase the converter, one needs to ensure that the RMS and surge overall efficiency. The freewheeling diode should be ratings are not exceeded. For generic tantalum turned on and off fast with minimum reverse recovery capacitors, it is suggested to derate their voltage ratings because the SC4521 is designed for high frequency at a ratio of about two to protect these input capacitors. applications. SS23 Schottky rectifier is recommended for certain applications. The average current of the diode, Boost Capacitor and its Supply Source Selection I _ can be calculated by: D AVG The boost capacitor selection is based on its discharge I = I ⋅(I − D) D-AVG omax ripple voltage, worst case conduction time and boost current. The worst case conduction time T can be w estimated as follows:  2007 Semtech Corp. 8 www.semtech.com SC4521 POWER MANAGEMENT Application Information (Cont.) Where: Thermal Considerations R – Load and L C – Output capacitor. There are three major power dissipation sources for the The goal of the compensation design is to shape the loop SC4521. The internal switch conduction loss, its switching loss due to the high frequency switching actions and the to have a high DC gain, high bandwidth, enough phase base drive boost circuit loss. These losses can be margin, and high attenuation for high frequency noises. estimated as: Figure 3 gives a typical compensation network which offers 2 poles and 1 zero to the power stage: 10 2 −3 P = I ⋅R ⋅D +10.8 ⋅10 ⋅I ⋅ V + ⋅I ⋅D ⋅(V ) total o on o I o boost 1000 S SC C45 4521 21 Where: L1 L1 Vo Vout ut 2 2 3 3 IN IN SW SW I = load current; O C C 5 5 6 6 R1 R1 R = on-equivalent resistance of the switch; EN EN FB FB on V = input voltage or output based on the boost circuit 8 8 7 7 SS SS CO COM MP P BOOST connection. C4 C4 R2 R2 The junction temperature of the SC4521 can be C5 C5 further determined by: R3 R3 D2 D2 T = T +θ ⋅ P J A JA total θ is the thermal resistance from junction to ambient. JA Its value is a function of the IC package, the application Figure 3. Compensation network provides 2 poles and layout and the air cooling system. 1 zero. The freewheeling diode also contributes a significant The compensation network gives the following portion of the total converter loss. This loss should be characteristics: minimized to increase the converter efficiency by using Schottky diodes with low forward drop (V ). F s 1+ P = V ⋅I ⋅(1− D) ω R diode F o 2 Z G (s) =ω ⋅ ⋅g ⋅ COMP 1 m s R + R 1 2 s ⋅(1+ ) ω P2 Loop Compensation Design Where: The SC4521 has an internal error amplifier and requires 1 ω = 1 a compensation network to connect between the COMP C + C 4 5 pin and GND pin as shown in Figure 3. The compensation 1 network includes C4, C5 and R3. R1 and R2 are used to ω = Z R ⋅ C program the output voltage according to: 3 4 R C + C 1 4 5 V = 0.8 •(1+ ) ω = O P2 R R ⋅ C ⋅ C 2 3 4 5 Assuming the power stage ESR (equivalent series resistance) zero is an order of magnitude higher than the closed loop bandwidth, which is typically one tenth of The loop gain will be given by: the switching frequency, the power stage control to output s 1+ transfer function with the current loop closed (Ridley R R 1 ω −3 L 2 Z T(s) = G (s) ⋅G (s) = 3.655 ⋅10 ⋅ ⋅ ⋅ COMP VD s s model) for the SC4521 will be as follows: C R + R s 4 1 2 (1+ ) ⋅(1+ ) ω ω P1 P2 4.3 ⋅R L G (s) = VD Where: s 1+ 1 1 ω = p1 R ⋅ C L R ⋅ C L  2007 Semtech Corp. 9 www.semtech.com 4 4 1 1 GN GND D BS BST T SC4521 POWER MANAGEMENT Application Information (Cont.) One integrator is added at origin to increase the DC gain. 2. Start the PCB layout by placing the power components ω is used to cancel the power stage pole ω so that the first. Arrange the power circuit to achieve a clean Z P1 loop gain has –20dB/dec rate when it reaches 0dB line. power flow route. Put all power connections on one ω is placed at half switching frequency to reject high side of the PCB with wide copper filled areas if P2 frequency switching noises. Figure 4 gives the asymptotic possible. diagrams of the power stage with current loop closed 3. The V bypass capacitor should be placed next to IN and its loop gain. the V and GND pins. IN 4. The trace connecting the feedback resistors to the output should be short, direct and far away from any noise sources such as switching node and switching components. Loop gain T(s) 5. Minimize the loop including input capacitor, the SC4521 and freewheeling diode D . This loop passes ω p1 2 Power stage high di/dt current. Make sure the trace width is wide ω enough to reduce copper losses in this loop. ω C P2 6. Maximize the trace width of the loop connecting the ω Z inductor, freewheeling diode D and the output 2 capacitor. 7. Connect the ground of the feedback divider and the compensation components directly to the GND pin Figure 4. Asymptotic diagrams of power stage with of the SC4521 by using a separate ground trace. current loop closed and its loop gain. 8. Connect Pin 4 to a large copper area to remove the IC heat and increase the power capability of the The design guidelines for the SC4521 applications are SC4521. A few feedthrough holes are required to as following: connect this large copper area to a ground plane to further improve the thermal environment of the 1. Set the loop gain crossover corner frequency ω for SC4521. The traces attached to other pins should C be as wide as possible for the same purpose. given switching corner frequency ω = 2πf C C 2. Place an integrator at the origin to increase DC and low frequency gains. 3. Select ω such that it is placed at ω to obtain a Z P1 -20dB/dec rate to go across the 0dB line. 4. Place a high frequency compensator pole ω (ω = πf ) to get the maximum attenuation of P2 P2 s the switching ripple and high frequency noise with the adequate phase lag at ω C. Layout Guidelines: In order to achieve optimal electrical and thermal performance for high frequency converters, special attention must be paid to the PCB layouts. The goal of layout optimization is to identify the high di/dt loops and minimize them. The following guidelines should be used to ensure proper operation of the converters. 1. A ground plane is suggested to minimize switching noises and trace losses and maximize heat transferring.  2007 Semtech Corp. 10 www.semtech.com SC4521 POWER MANAGEMENT Application Information (Cont.) Design Example 1: 5V to 1V at 2A D1 D1 C1 C1 0. 0.2 22 2u u L1 L1 V V = 5 = 5V V I I V V =1 =1V @2 V @2A A R0 R0 o o 2 2 3 3 IN IN SW SW 3. 3.9 9u uH H 0 0 C3 C3 Co Co 10u 10u 5 5 6 6 R1 R1 470 470u u EN EN FB FB 2. 2.4 49 9k k 8 8 7 7 SS SS CO COM MP P Cs Css s SC SC4521 4521 C4 C4 R2 R2 100 100n n 18n 18n 10k 10k C5 C5 560 560p p R3 R3 20k 20k D2 D2 Note: The bottom pad needs a big copper area to remove the heat. Bill of Materials Iy temQe tRe eferenc Vr alu Part No./Manufacture 11CR 1 0X .22uF, 25V, 0805, X7 Vishay: VJ0805Y224KX 21CA o 4n 70uF, 10V, Z Rubico 31CF 3 1T 0u TDK: C3216OJ106M 41CV 4 1y 8nF, 0805, X7R, 25 Visha 51C5 5 5y 60pF, 50V, 080 Visha 61D3 1 1N4148SW, SOD32 71D2 2 E. C30LA0 Nihon Inter Electronics Corp 81LH 1 3L .9u Sumida: RCR875DNP-3R9 91R5 0 0, 080 11 0R5 1 2E .49k, 1%, 080 SMTZON 11 1R5 2 10k, 1%, 080 11 2R5 3 20k, 1%, 080 1- 3R5 4 not used, 080 11 4CF ss 100n 11 5U1 1 Sh C452 Semtec Unless specified, all resistors have 1% precision with 0805 package. Resistors are +/-1% and all capacitors are +/-20%  2007 Semtech Corp. 11 www.semtech.com 1 1 4 4 GN GND D BST BST SC4521 POWER MANAGEMENT Application Information (Cont.) Design Example 2: 6.2V to 1.5V at 1.5A D1 C1 0.22u L1 V = 6.2V V =1.5V I R0 o 2 3 IN SW 0 4.7uH C3 Co 5 6 R1 10u 100u EN FB 8.66k 8 7 SS COMP Css SC4521 C4 R2 100n 18n 10k C5 560p R3 4.87k D2 Note: The bottom pad needs a big copper area to remove the heat. Bill of Materials Iy temQe tRe eferenc Vr alu Part No./Manufacture 11CR 1 0X .22uF, 25V, 0805, X7 Vishay: VJ0805Y224KX 21CF o 1o 00u Sany 31CF 3 1T 0u TDK: C3216OJ106M 41CV 4 1y 8nF, 0805, X7R, 25 Visha 51C5 5 5y 60pF, 50V, 080 Visha 61D3 1 1N4148SW, SOD32 71D3 2 MN BRA210LT O 81LH 1 47 .7u Toko: 919AS-4R 91R5 0 0y , 080 Visha 11 0R5 1 8y .66k, 1%, 080 Visha 11 1R5 2 1y 0k, 1%, 080 Visha 11 2R5 3 4y .87k, 080 Visha 1- 3R5 4 not used, 080 11 4CF ss 100n 11 5U1 1 Sh C452 Semtec Unless specified, all resistors have 1% precision with 0805 package. Resistors are +/-1% and all capacitors are +/-20%  2007 Semtech Corp. 12 www.semtech.com 1 4 GND BST SC4521 POWER MANAGEMENT Application Information (Cont.) Design Example 3: 13V ~ 21V to 3.3V at 1A D3 D3 C1 C1 0. 0.2 22 2u u L1 L1 V V V V =3. =3.3 3V V I I R0 R0 o o 2 2 3 3 IN IN SW SW 10u 10uH H 0 0 C2 C2 C3 C3 Rs Rss s 5 5 6 6 R1 R1 10u 10u 4. 4.7 7u u EN EN FB FB 200 200k k 24. 24.9k 9k 8 8 7 7 SS SS CO COM MP P Cs Css s SC SC4521 4521 R2 R2 C4 C4 330 330n n 18n 18n 8. 8.2 25 5k k C5 C5 560 560p p R3 R3 3. 3.8 83 3k k D2 D2 Note: The bottom pad needs a big copper area to remove the heat. Bill of Materials Iy temQe tRe eferenc Vr alu Part No./Manufacture 11CR 1 0X .22uF, 25V, 0805, X7 Vishay: VJ0805Y224KX Taiyo-Yuden: 21CF 2 10u EDK316BJ106MF-T 31CR 3 4c .7uF, 1206, 25V, X5 Panasoni 41CV 4 1y 8nF, 0805, X7R, 25 Visha 51C5 5 5y 60pF, 50V, 080 Visha 61 D2 Nihon-International: EC31QS04 71D3 3 1N4148WS, SOD32 Sumida: 81LH 1 10u CDRH6D38NP-100NC 91R5 0 0, 080 11 0R5 1 2E 4.9k, 1%, 080 SMTZON 11 1R5 2 8E .25k, 1%, 080 SMTZON 11 2R5 3 3E .83k, 1%, 080 SMTZON 1- 3R5 ss 200k, 080 11 4C5 ss 330nF, 080 11 5U1 1 Sh C452 Semtec Unless specified, all resistors have 1% precision with 0805 package. Resistors are +/-1% and all capacitors are +/-20%  2007 Semtech Corp. 13 www.semtech.com 4 4 1 1 GN GND D BS BST T SC4521 POWER MANAGEMENT Application Information (Cont.) Design Example 4: 13V ~ 21V to 5V at 1.5A D3 D3 C1 C1 0. 0.2 22 2u u L1 L1 V V V V =5 =5V V I I R0 R0 o o 2 2 3 3 IN IN SW SW 10u 10uH H 0 0 C2 C2 C3 C3 Rs Rss s 5 5 6 6 R1 R1 10u 10u 4. 4.7 7u u EN EN FB FB 200 200k k 51. 51.1k 1k 8 8 7 7 SS SS CO COM MP P Cs Css s SC SC4521 4521 470 470n n R2 R2 C4 C4 18n 18n 10k 10k C5 C5 560 560p p R3 R3 4. 4.8 87 7k k D2 D2 Note: The bottom pad needs a big copper area to remove the heat. Bill of Materials Iy temQe tRe eferenc Vr alu Part No./Manufacture 11CR 1 0X .22uF, 25V, 0805, X7 Vishay: VJ0805Y224KX Taiyo-Yuden: 21CF 2 10u EDK316BJ106MF-T 31CR 3 4c .7uF, 1206, 25V, X5 Panasoni 41CV 4 1y 8nF, 0805, X7R, 25 Visha 51C5 5 5y 60pF, 50V, 080 Visha 61 D2 Nihon-International: EC31QS04 71D3 3 1N4148WS, SOD32 Sumida: 81LH 1 10u CDRH6D38NP-100NC 91R5 0 0, 080 11 0R5 1 5E 1.1k, 1%, 080 SMTZON 11 1R5 2 1E 0k, 1%, 080 SMTZON 11 2R5 3 4E .87k, 1%, 080 SMTZON 1- 3R5 ss 200k, 080 11 4C5 ss 470nF, 080 11 5U1 1 Sh C452 Semtec Unless specified, all resistors have 1% precision with 0805 package. Resistors are +/-1% and all capacitors are +/-20%  2007 Semtech Corp. 14 www.semtech.com 4 4 1 1 GN GND D BS BST T SC4521 POWER MANAGEMENT Application Information (Cont.) (PCB - TOP) (PCB - BOTTOM)  2007 Semtech Corp. 15 www.semtech.com SC4521 POWER MANAGEMENT Application Information (Cont.) (Componet Side - TOP) (Componet Side - TOP)  2007 Semtech Corp. 16 www.semtech.com SC4521 POWER MANAGEMENT Outline Drawing - SOIC-8L EDP A D e DIMENSIONS N INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX - - A .053 .069 1.35 1.75 2X E/2 - - A1 .000 .005 0.00 0.13 - - A2 .049 .065 1.25 1.65 E1 E - - b .012 .020 0.31 0.51 - - c .007 .010 0.17 0.25 D .189 .193 .197 4.80 4.90 5.00 12 E1 .150 .154 .157 3.80 3.90 4.00 E .236 BSC 6.00 BSC ccc C e .050 BSC 1.27 BSC 2X N/2 TIPS e/2 F .116 .120 .130 2.95 3.05 3.30 H .085 .095 .099 2.15 2.41 2.51 B - - h .010 .020 0.25 0.50 L .016 .028 .041 0.40 0.72 1.04 D (.041) (1.05) L1 N 8 8 aaa C - - 01 0° 8° 0° 8° A2 A aaa .004 0.10 SEATING bbb .010 0.25 PLANE ccc C A1 .008 0.20 bxN bbb C A-B D h F EXPOSED PAD h H H c GAGE PLANE 0.25 L 01 (L1) DETAIL A SEE DETAIL A SIDE VIEW NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS AND TO BE DETERMINED AT DATUM PLANE -A- -B- -H- 3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. REFERENCE JEDEC STD MS-012, VARIATION BA. 4.  2007 Semtech Corp. 17 www.semtech.com SC4521 POWER MANAGEMENT Land Pattern - SOIC-8L-EDP E SOLDER MASK D DIMENSIONS DIM INCHES MILLIMETERS (.205) (5.20) C Z (C) D .134 3.40 G F E .201 5.10 F .101 2.56 G .118 3.00 Y P .050 1.27 X .024 0.60 THERMAL VIA P Y .087 2.20 Ø 0.36mm X Z .291 7.40 NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 2. REFERENCE IPC-SM-782A, RLP NO. 300A. 3. 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 Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804  2007 Semtech Corp. 18 www.semtech.com