SEMTECH SC4911

SC4911 Bias/Primary Side PWM Controller with Ultra Low Start-up Current POWER MANAGEMENT Description Features The SC4911 is a highly integrated bias/primary side PWM ‹ Programmable switching frequency up to 500kHz controller designed for off-line or isolated dc-dc convert- ‹ Line UVLO Protection ers in telecommunication and data communication ap- ‹ Undervoltage Lockout plications. The high degree of integration minimizes the ‹ Low startup current (45µA) amount of discrete parts needed and leads to substan- ‹ Cycle by cycle current limit tial cost and space saving converter designs. ‹ 8 pin MSOP. Available in Lead-free, fully WEEE and RoHS compliant The circuitry of the SC4911 includes line voltage UVLO featuring startup current less than 50µA and program- Applications mable switching frequency. The device supply is derived ‹ Telecom isolated converters from an auxiliary winding on the transformer. The auxil- ‹ Offline isolated power supplies iary winding could also provide output feedback informa- ‹ Instrumentation power supplies tion if an optocoupler is not used. ‹ Battery chargers Typical Application Circuit D1 T1 D2 C1 Vout R1 Vin C2 R2 C3 R3 C4 R4 C5 C6 R5 U1 SC4911 Q1 3 7 FB OUT R6 4 5 COMP ILIM R7 C7 C8 R8 R9 Revision: April 5, 2006 1 www.semtech.com 2 1 RT LUVLO 6 8 GND VCC SC4911 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. Pl arameter Sm ymboMs aximu Unit SV upply Voltage 1V 8 CC SI upply Current 2A 0 m CC Line UVLO Voltage V V CC FB, ILIM and COMP -V 0.3 to 6 Output Current Source or Sink 2A 50 m ST torage Temperature Range -C 60 to +150 ° STG JT unction Temperature Range -C 40 to +150 ° J LT ead Temperature (Soldering) 10 Sec. 2C 60 ° LEAD ED SD Rating (Human Body Model) E2 S kV Electrical Characteristics Unless specified: T = T = -40°C to +125°C, V = 12V, R = 100KΩ, V = 2.4V, LUVLO = 1.5V. A CC FB J T Ps arameter Tn est Condition Mp i Tx y Mt a Uni Power Supply Vcc Turn-On Voltage 60 .0 7V . Of perating Current =4 200kHz, No load 30 . 5A . m s SO tartup Current L= UVL05 .6V 408A µ VI CC Zener Shunt Voltage =5 10mA 16171V CC Line UVLO Lockout Threshold 15 .22 18 .2 1V .2 UVLO Hysteresis 7V 0 m BV ias Current <0 1.25V 1A 0 n LUVLO Error Amplifier FV eedback Input Voltage =4 12V 20 .4 26 .5 2V .5 CC FV eedback Input Voltage Regulation =5 7V to 12V25 .42 2V .57 CC Input Bias Current 1A 70 n Amplifier Transconductance 1o 000 µmh Amplifier Souce Current 5A 00 µ Amplifier Sink Current 6A 00 µ Open Loop Voltage Gain 5B 0 d  2006 Semtech Corp. 2 www.semtech.com SC4911 POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: T = T = -40°C to +125°C, V = 12V, R = 100KΩ, V = 2.4V, LUVLO = 1.5V. A CC FB J T Ps arameter Tn est Condition Mp i Tx y Mt a Uni Oscillator FR requency Range = 200kΩ 100 T kHz R = 43 kΩ 500 T Frequency 10 70 20 0 2z 3 kH Duty Cycle Maximum Duty Cycle 55 7 627% MV inimum Duty Cycle =0 3V % FB Current Limit Current Limit Threshold 55 00 50 2 5V 5 m Propagation Delay to Gate 7S 0 n Output OA utput Voltage Low State S1 ink 5m 05 . 0V . OA utput Voltage High State S5 ource 5m 92 .1V 0. RC ise Time =5 100pF 2S n OUT FC all Time =0 100pF 1S n OUT  2006 Semtech Corp. 3 www.semtech.com SC4911 POWER MANAGEMENT Pin Configuration Ordering Information Pe art NumberPT ackag Temp. Range ( ) J TOP VIEW SC4911IMSTR (1) MSOP-8 -40°C to +125°C (2) SC4911IMSTRT LUVLO VCC Notes: RT OUT (1) Only available in tape and reel packaging. A reel contains 2500 devices. FB GND (2) Lead free product. This product is fully WEEE and RoHS compliant. COMP ILIM (MSOP- 8 PIN) Pin Descriptions Pe in #Pn in Nam Pin Functio 1OL. UVL Line under voltage lockout 2TR. For programming oscillator frequency 3BF. Feedback 4PC. OM Feedback compensation 5MI. LI Current limit sense 6DG. N Ground 7TO. U Gate drive output. Low during UVLO or LUVLO 8CV. C Supply voltage Marking Information Part Number Code (Example: AAxx) yyww = Date Code (Example: 0012) xxxx = Semtech Lot No. (Example: E901 xxxx 01-1)  2006 Semtech Corp. 4 www.semtech.com SC4911 POWER MANAGEMENT Block Diagram Vcc RT Startup & L-Uv lo Oscillator Uvlo Comp Output Logic Driver Out BandGap + + - PWM Latch FB - PWM Comparator Error Amplifier Comp OR gate ILIM Ilim Comparator Vt 0. 0.525V 5V Gnd  2006 Semtech Corp. 5 www.semtech.com + - SC4911 POWER MANAGEMENT Applications Information The SC4911 is a voltage mode controller designed mainly The bias current consumed by the device during this pe- for the isolated or non-isolated flyback converters. As riod is only typical 30µA. Once Vcc exceeds the turn-on shown in the Block Diagram, it includes start-up circuit, voltage, OUT starts driving the MOSFET, transferring en- bandgap, error amplifier, PWM comparator, logic and ergy to the secondary and the bias output. If the bias output stage. Line undervoltage has dual functions of output voltage builds to and is above the Vcc turnoff line voltage lockout and shutdown. When LUVLO is pull voltage, the start-up is completed and normal operation down to ground, the SC4911 is disabled and the quies- begins. cent current is reduced to typical 30µA. When it is con- The size of the start-up resistor not only affects power nected to a resistor voltage divider between input volt- supply start-up time, but also power supply efficiency. age and ground, it monitors the line voltage. The resistor dissipates continuous power in normal op- eration. Due to ultra low start-up current of the SC4911, Oscillator large value resistor (several hundred Kohm to 1Mohm) The switching frequency of the SC4911 is set by an ex- could be used, particularly for off-line applications to ternal resistor connected between RT and GND. Figure improve efficiency considering reasonable start-up time. 1 shows the relationship between the resistance of the external resistor and the switching frequency. Current Limit The current sense resistor is selected by dividing the cur- Figure 1. Timing Resistor vs Oscillator Frequency rent sense threshold voltage 0.525V by the primary peak current at the desired current limit point, typically 120% of the primary peak current. Timing Resistor vs Switching Frequency 0.525V R = SENSE 250 1.2 × I PK 200 Care must be taken to ensure proper selection of sense 150 resistor and good layout to prevent erratic operation. The non-inductive resistor must be used as the sense resis- 100 tor. Parasitic inductance in series with the sense resistor 50 must be minimized. Additional RC filter may be neces- 0 sary to eliminate the narrow spike time on the leading 100 200 300 400 500 edge of the primary current. The RC time constant can Frequency ( KHz ) be chosen to be equal to the time constant of the sense resistor and the parasitic inductance. Line UVLO and VCC UVLO PCB Layout The Line UVLO monitors the input line voltage and VCC Long power supply and ground traces should be avoided. UVLO monitors the supply voltage to the SC4911. If ei- A 0.1µF ceramic capacitor closely placed between Vcc ther input line or VCC is below the lockout threshold, the output is held low and the supply current to the chip is and GND is recommended. The timing resistor used to typically 30µA. program switching frequency should be located close to A resistor divider from the input line to GND determines pin RT and pin GND in order to have a stable switching the desired undervoltage lockout level. To prevent noise frequency. MOSFET should be located near the device coupling to affect proper UVLO operation, a small capaci- and a resistor in the range of several ohms could be tor, one hundred to a few hundred pF, is recommended used in series with the gate drive to damp the ringing if to be used from Line UVLO pin to GND. the trace between the drive output and MOSFET is not short enough. Star ground connection is recommended Start-up to avoid ground loops. The Power path for input filter, As shown in Typical Applications Circuit on the front page, MOSFET and transformer should be separated from when input voltage is applied, C1 is trickle charged signal path for timing resistor and feedback resistor, through the start-up resistor R1 until the SC4911 Vcc and both should be brought to a single ground point. reaches the turn-on voltage.  2006 Semtech Corp. 6 www.semtech.com Resistance ( Kohms ) SC4911 POWER MANAGEMENT Typical Applications 48V TO 12V FLYBACK CONVERTER AS AUXILIARY SUPPLY The output of the T1 bias winding is rectified, filtered by Figure 2 shows a simple bias supply using the SC4911. This 36 - 72V input flyback power supply employs primary C1 and is fed to the FB through feedback resistor R5 side regulation from the transformer bias winding, which and R7. The output voltage on the secondary is eliminates the need of opto coupler and secondary proportional to the bias voltage by the turns ratio of the reference error amplifier. This is best for low cost output to the bias winding. C7 and R9 are for frequency applications requiring isolation and narrow load variation compensation. An additional small capacitor could be range on the secondary. used from COMP to GND if it is needed. The LUVLO pin monitors the input voltage via resistor R2 and R4 to During the start-up, the input source trickle charges the determine turn-on and turn-off of the converter. Capacitor capacitor C1 through start-up resistor R1. As long as C5 helps filter out the noise from the input line. voltage across C1 reaches the Vcc turn-on threshold, the SC4911 turns on abruptly and start driving the gate of MOSFET Q1. After the SC4911 starts up the primary bias winding supplies the primary circuitry. Vpri = 12V D1 1N5819 T1 2 C1 D2 1N5819 Vo = 12V R1 10uF 1 8 100K Vin = 48V C2 3 100uF 10 R2 C3 2.7MEG R3 10uF 5 68 C4 R4 C6 C5 0.1uF 100K 150pF 100pF R5 383K 1 8 U1 SC4911 LUVLO VCC Q1 3 7 Si2320DS FB OUT R6 4 5 COMP ILIM 51 R7 C7 100K RT GND C8 47nF R8 2 6 1000pF 1.00 R9 4.7K R10 100K Figure 2. 48V to 12V Flyback Converter as Auxiliary Supply  2006 Semtech Corp. 7 www.semtech.com SC4911 POWER MANAGEMENT Typical Applications (Cont.) Isolated feedback 48V to 12V application Figure 3 gives an example of isolated feedback and low Timing resistor R13 sets switching frequency. R3 and power flyback application of the SC4911. T1 is a three C6 are used to suppress the voltage spikes across the winding transformer. The winding 1-2 is a bias winding switch due to leakage inductance of T1. R11 is current which supplies the primary circuitry after the SC4911 sense resistor to set current limit of the convertor. R10 starts up. During the startup, the input source trickle and C9 filter spikes caused by parasitic capacitance charges the capacitor C1 through the start-up resistor during the turning on of Q1. The U3 SC431 is shunt R1. As long as voltage across C1 reaches the Vcc turn- regulator integrating an accurate 2.5V bandgap on threshold, the SC4911 turns on abruptly and start reference, op amp and driver into a single device. It driving the gate of MOSFET Q1. As Q1 starts switching, compares sensed output voltage divided by R7 and R9 regenerative feedback from the bias winding will provide to its internal reference and drives the amplified error current via D1 to capacitor C1. signal to opto-coupler U1. C7 keeps ripple and noise In this configuration, the input voltage is in the range of from over driving the device. U1 delivers the isolated 36V to 72V for telecom applications, and the LUVLO pin feedback signal to the SC4911. C8 and R12 are for monitors the input voltage via resistor R2 and R5 to compensation. An additional small capacitor could be determine turn-on and turn-off of the converter. Capacitor used from COMP to GND if needed. C5 helps filter out the noise from the input line. D1 1N5819 T1 2 C1 Vo = 5V R1 D2 1N5819 10uF 1 8 100K Vin = 48V C2 3 10 100uF C3 R2 10uF 2.7MEG R3 5 68 R4 330 C4 U1 R5 C6 C5 0.1uF NEC2501 100K 150pF 100pF R6 1K U2 SC4911 1 8 R7 10K LUVLO VCC C7 Q1 U3 220pF 3 7 Si2320DS FB OUT SC431 R8 1K R9 R10 4 5 10K COMP ILIM 51 C8 GND RT C9 47nF R11 1000pF 1.00 6 2 R12 4.7K R13 100K Figure 3. Isolated 48V to 12V Flyback Converter  2006 Semtech Corp. 8 www.semtech.com SC4911 POWER MANAGEMENT Typical Applications (Cont.) Non-Isolated feedback 48V to 12V application Figure 4 is an example of low cost, non-isolated feedback, In this 36V to 72V telecom application, LUVLO monitors low power application of the SC4911. T1 is a two winding the input voltage via resistor R2 and R4 to determine transformer. The output voltage is directly fed to the turn-on and turn-off of the converter. Capacitor C4 helps primary circuitry. filter out the noise from the input line. Voltage feedback is directly brought from the output to the input error During the start-up, the input source trickle charges the amplifier of SC4911 through R5 and R7. C6 and R9 are capacitor C3 through start-up resistor R1. As long as the for frequency compensation. An additional small voltage across C3 reaches the Vcc turn-on threshold, capacitor could be used from COMP to GND if needed. the SC4911 turns on abruptly and starts driving the gate of MOSFET Q1. After the SC4911 starts up the secondary winding supplies the primary circuitry. D1 1N5819 R1 Vin = 48V Vo = 12V 100K D2 1N5819 T1 C1 R2 C2 2.7MEG R3 47uF 10uF 68 C3 R4 C5 C4 100K 10uF 150pF 100pF R5 383K U1 SC4911 1 8 LUVLO VCC Q1 3 7 Si2320DS FB OUT R6 4 5 COMP ILIM 51 R7 C6 100K RT GND 47nF C7 R8 1000pF 2 6 1.00 R9 4.7K R10 100K Figure 4. Non-isolated 48V to 12V Flyback Converter  2006 Semtech Corp. 9 www.semtech.com SC4911 POWER MANAGEMENT Typical Applications (Cont.) 48V to 12V FLYBACK CONVERTER AS BATTERY CHARGER In this application, voltage feedback is directly brought Figure 5 is another example of non-isolated feedback, from the output to the input error amplifier of SC4911 low power and compact application of the SC4911 as a through R4 and R7. C5 and R9 are for frequency battery charger. Battery charging rate is determined by compensation. current sense resistor R8. LUVLO is used to not only turn on or turn off the charger by battery charge controller, but also monitors the input line voltage via resistor R2 and R5 to determine turn-on and turnoff of the converter. During the start-up, the input source trickle charges the capacitor C3 through start-up resistor R1. As long as voltage across C3 reaches the Vcc turn-on threshold, the SC4911 turns on abruptly and starts driving the gate of MOSFET Q1. After the SC4911 starts up the secondary winding supplies the primary circuitry. D1 1N5819 R1 Vin = 48V To 12V Battery 100K D2 1N5819 T1 C1 R2 C2 47uF 2.7MEG R3 10uF R4 68 C3 619K R5 10uF C4 100K 150pF U1 SC4911 1 8 To Battery Charger Controller VCC LUVLO Q1 3 7 Si2320DS FB OUT R6 4 5 COMP ILIM 51 R7 C5 100K RT GND 47nF C6 R8 1000pF 1.00 2 6 R9 4.7K R10 100K Figure 5. 48V to 12V Flyback Converter as Battery Charger  2006 Semtech Corp. 10 www.semtech.com SC4911 POWER MANAGEMENT Evaluation Board Schematic D1 T1 J3 1N5819HW 31414R 2 Vb=12V 1 2 C1 J1 D3 D2 B150 47uF 1 5 1N5819HW Vo=12V 1 J2 2 C2 C3 3 Vin=48V 1 47uF 47uF 8 2 C4 R2 R1 10uF/100V 2.7MEG 100K R3 4 68 C5 R4 C6 10uF 100K C7 470pF R5 150pF/100V 383K 1 U1 SC4911 8 LUVLO VCC Q1 R6 3 7 Si2320DS FB OUT 0 R7 4 5 COMP ILIM 51 R8 C8 100K C10 RT GND C9 47nF R9 470pF 1000pF 2 1.00 6 R10 R11 4.99K 100K  2006 Semtech Corp. 11 www.semtech.com SC4911 POWER MANAGEMENT Evaluation Board Schematic- BOM Iy temQe uantitRn eferencP# art/DescriptioMt anufacturer Foot Prin 13CF 1, C2, C3 4M 7u13 6TPB47 SM/CT 734 21CV 4 10 0uF/100E1 EU-FC2A10 CYL/D.250/LS.100/.03 31CF 5 1L 0uG0 RM32ER61C106KC31 SM/C 121 41CF 645 70p SM/C 080 61CV 715 50pF/100 SM/C 080 62CF 8, C1045 7n SM/C 080 71CF 915 000p SM/C 080 82DW 1, D313 N5819H SOD12 91D3 2BA 150-1 SM/SM 11 0QS 1 S1 i2320DS3 i2320DS-T SOT-2 14 1RK 1, R4, R8, R1115 00 SM/R 080 11 2RG 225 .7 ME SM/R 080 11 3 R8 3 65 SM/R 080 11 4RK 535 83 SM/R 080 11 5 R0 6 SM/R 0805 11 6R1 7 55 SM/R 080 11 7 R1 9 SM/R 0805 11 8RK 1045 .99 SM/R 080 11 9TR 1 3M 1414 MR IDCO 31414 Semtech Corp. 21 0UR 1 SC4911IMST MSOP-8 805-498-2111  2006 Semtech Corp. 12 www.semtech.com SC4911 POWER MANAGEMENT Typical Characteristics Oscillator Frequency vs Temperature Vcc Turn-On Voltage vs Temperature 200.00 5.80 Rt = 100k 199.00 5.70 198.00 5.60 197.00 196.00 5.50 195.00 5.40 194.00 193.00 5.30 192.00 5.20 191.00 190.00 5.10 -40 -20 0 20 40 60 80 100 120 -40 -20 0 20 40 60 80 100 120 Temperature (°C) Temperature (°C) Vcc Zener Shunt Voltage vs Temperature Line UVLO Lockout Threshold vs Temperature 16.04 1.245 1.244 16.02 1.243 16.00 1.242 15.98 1.241 15.96 1.240 1.239 15.94 1.238 15.92 1.237 15.90 1.236 -40 -20 0 20 406080 100 120 -40 -20 0 20 40 60 80 100 120 Temperature (°C) Temperature (°C) Max. Duty Cycle vs Temperature Error Amplifier Feedback Voltage vs Temperature 66.50 2.525 66.00 2.520 65.50 2.515 65.00 2.510 64.50 2.505 64.00 2.500 63.50 2.495 63.00 2.490 -40 -20 0 2040 6080 100 120 -40 -20 0 20 40 60 80 100 120 Temperature (°C) Temperature (°C) Current Limit Threshold vs Temperature 528 527 526 525 524 523 522 521 520 -40 -20 0 2040 6080 100 120 Temperature (°C)  2006 Semtech Corp. 13 www.semtech.com Zener Shunt Voltage (V) Turn On Voltage (V) Threshold (mV) Max. Duty Cycle (%) Lockout Threshold (V) Feedback Input Voltage (V) Frequency (kHz) SC4911 POWER MANAGEMENT Outline Drawing - MSOP-8 DIMENSIONS e/2 INCHES MILLIMETERS DIM MIN NOM MAX MIN NOM MAX A - - - - A .043 1.10 D - - A1 .000 .006 0.00 0.15 N A2 .030 - .037 0.75 - 0.95 b .009 - .015 0.22 - 0.38 c - - .003 .009 0.08 0.23 2X E/2 D .114 .118 .122 2.90 3.00 3.10 E1 .114 .118 .122 2.90 3.00 3.10 E1 E E .193 BSC 4.90 BSC PIN 1 e .026 BSC 0.65 BSC INDICATOR L .016 .024 .032 0.40 0.60 0.80 L1 (.037) (.95) N 8 8 ccc C 12 01 0° - 8° 0° - 8° 2X N/2 TIPS e aaa .004 0.10 bbb .005 0.13 B ccc .010 0.25 D H aaa C A2 A c SEATING GAGE PLANE PLANE A1 C bxN 0.25 L 01 bbb C A-B D (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. 4. REFERENCE JEDEC STD MO-187, VARIATION AA. Land Pattern - MSOP-8 X DIMENSIONS DIM INCHES MILLIMETERS C (.161) (4.10) G .098 2.50 (C) G Z P .026 0.65 X .016 0.40 Y .063 1.60 Z .224 5.70 Y P NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804  2006 Semtech Corp. 14 www.semtech.com