PRELIMINARY .eatures Synchronous rectification with adaptive cont

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PRELIMINARY .eatures Synchronous rectification with adaptive cont

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High Performance Secondary Side Controller with Synchronous Rectifier
PRELIMINARY .eatures
Synchronous rectification with adaptive control Programmable secondary side delay Programmable switching frequency Programmable max. duty cycle Remote voltage sense capability Soft start with active shutdown 0.75V precision reference output applications Oscillator sychronization Undervoltage Lockout Operation 1MHz Current-mode voltage-mode operation Single stage power conversion with multiphase link capability (with SC4201) TSSOP package
SC4910A/B
SC4910A/B integrated, full featured, secondary side controller designed single ended isolated switch mode power supplies with synchronous rectification where efficiency fast transient response primary concern. SC4910A/B outputs both primary secondary synchronous rectification. primary drive output designed drive small cost pulse transformer isolate primary driver. secondary control makes much easier monitor control system load with tight control loops implement load current sharing synchronous rectification. SC4910A/B features synchronous rectification, multiphase link capability, programmable secondary side delay, programmable switching frequency programmable maximum duty cycle. designed either current-mode voltage-mode operation. SC4910A typical turn-on threshold SC4910B threshold 4.5V
Applications
Telecom isolated converters Isolated VRMS Networking power supplies Industrial power supplies Distributed power architectures High density power modules
Typical Application Circuit
+Vin
LOAD
SC1301 SC1301
+12V SC1301 VREF AGND PGNDA OUTA DELAY PHASE OUTB COMP SYNC/EN -SENSE PGNDB PVCCB PVCCA AVCC ISHARE SC4910
Revision April 2002
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SC4910A/B
POWER MANAGEMENT Absolute Maximum Ratings
Parameter Supply Voltage Output Voltage OUTA OUTB Current Source Sink Analog Input Voltage Ambient Temperature Range Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) Sec. TSTG TLEAD Symbol Maximum +125 +150
PRELIMINARY
Exceeding specifications below result permanent damage device, device malfunction. Operation outside parameters specified Electrical Characteristics section implied.
Units
Electrical Characteristics
Unless specified: 25°C,
Parameter Supply Operating Current Undervoltage Lockout
Test Conditions
Unit
SYNC/EN
4910A Start Threshold 4910B 4910A UVLO Hysteresis 4910B VREF Reference 4910A Output Voltage 4910B Output Current Line Regulation Load Regulation Soft Start Output Voltage Accuracy Line Regulation Impedance
2002 Semtech Corp.
4.35
4.50
4.65
4.75 2.97
3.30
5.25 3.63
IREF
0.75
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SC4910A/B
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless specified: 25°C,
PRELIMINARY
Parameter Error Amplifier Input Bias Current Offset Voltage Open Loop Gain CMRR PSRR Output High Voltage Output Voltage Unity Gain Bandwidth Slew Rate Oscillator Frequency Range
Test Conditions
Unit
ICOMP 1.5mA ICOMP 1.5mA 1.75
V/µS
Frequency range Frequency range
1000
Frequency Peak Voltage Valley Voltage
50K,
Enable Input High Enable Input Duty Cycle Maximum Duty Cycle Minimum Duty Cycle Duty Cycle Tolerance Current Limit Cycle Cycle Threshold Shutdown Threshold Delay Output Input Impedance 50K,
0.975
1.025 1.25
1.075
2002 Semtech Corp.
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SC4910A/B
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless specified: 25°C,
PRELIMINARY
Parameter OUTA OUTB Output Output High Rise Time
Test Conditions
Unit
IOUTPUT 100mA IOUTPUT 100mA COUT 100pF COUT 100pF RDELAY PHASE 1.5V PHASE 1.5V
10.25
Fall Time Delay OUTB Falling OUTA Rising OUTA Falling OUTB Rising
Note: Guaranteed design. Guaranteed characterization.
2002 Semtech Corp.
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SC4910A/B
POWER MANAGEMENT Configurations
VIEW
-SENSE SYNC/EN VREF PHASE AGND PGNDA PGNDB OUTA COMP ISHARE DELAY AVCC PVCCA PVCCB OUTB
PRELIMINARY Ordering Information
Part Number SC4910AITSTR SC4910BITSTR ackag TSSOP-20 TSSOP-20 Temp. Range (TA) -40°C 85°C -40°C 85°C
Note: Only available tape reel packaging. reel contains 2500 devices.
TSSOP)
2002 Semtech Corp.
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SC4910A/B
POWER MANAGEMENT Descriptions
Name -SENSE SYNC/EN VREF PHASE AGND PGNDA PGNDB OUTA OUTB AVCC DELAY Remote voltage sense return. Bidirectional synchronization enable /disable pin. Referenced -SENSE. Soft start. Current sense input. internal reference output. Phase node synchronous rectification. Analog ground. Power ground OUTA. Power ground OUTB. Output driver primary MOSFET secondary forward MOSFET. during UVLO. Output MOSFET driving signal forward rectifier. during UVLO. Power supply OUTB. Power supply OUTA. Analog supply voltage. Predictive delay between OUTA OUTB. delay from turn-off freewheeling MOSFET turn-on forward MOSFET primary MOSFET. delay time 200nS programmable. Current share bus. Feedback compensation. Connect timing resistor control negative ramp internal oscillator. Connect timing resistor control positive ramp internal oscillator. Function
PRELIMINARY
ISHARE COMP
2002 Semtech Corp.
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SC4910A/B
POWER MANAGEMENT Block Diagram PRELIMINARY
2002 Semtech Corp.
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SC4910A/B
POWER MANAGEMENT Applications Information
SC4910A/B secondary side controller working either current mode voltage mode mainly applications forward converters with synchronous rectification. While OUTA drives primary MOS.ET through transformer secondary forward rectifier, OUTB drives secondary freewheeling rectifier. switching frequency maximum duty cycle programmable with resistors. delay time from falling edge OUTA rising edge OUTB adaptive monitoring phase node voltage. delay time from falling edge OUTB rising edge OUTA determined programming resistor from DELAY ground. ISHARE allows current sharing among parallel operating units make current equally distribute load. -SENSE separated from provides true output voltage remote sense capability. Other features include soft start, sychronization enable/disable user, provided reference voltage. Oscillator frequency duty cycle oscillator controlled placing resistors from pins ground. resistor controls maximum duty cycle resistor controls portion cycle. When resistor equal that RT2, maximum duty cycle will approximately 50%. following formula used determine time duration portions:
PRELIMINARY
SYNC/EN enable function looks SYNC/EN internal timing capacitor. SYNC/EN internal timing capacitor voltage high, then SC4910 disabled with OUTA, OUTB pulled low. When SYNC/EN held high, device enabled runs internal oscillator. When rising signal detected SYNC/EN one-shot triggered discharges internal timing capacitor. long internal timing capacitor below internal reference level, device will synchronize with external pulse. internal timing capacitor allowed charge internal reference level before another SYNC pulse detected, device will switch back internal oscillator. Soft Start connected internal reference, 0.75V, through internal resistor. also connected non-inverting input error amplifier. With external capacitor connected this pin, soft start timing will determined this time constant. During start-up, held until undervoltage lockout threshold reached. Once UVLO threshold reach, released device will regulate voltage this pin. Delays delay falling edge OUTB rising edge OUTA determined resistor from DELAY ground. following formula used determine delay time:
Current Sense Current Limit input impedance ohms swings from 1.0V 2.5V. With resistor from ground, device operates voltage mode with ramp that will swing from 0.2V 0.5V. When resistor connect voltage that proportional primary side current, device will operate current mode. cycle-by-cycle current limit triggered when voltage rises above exceeds 1.25V, faulty latch will outputs will driven low. soft start capacitor then discharged internal current sink. outputs allowed until soft start capacitor fully discharged 0.15V. this point fault latch will reset SC4910 will begin soft start process. This results hiccup current limit mode continuous fault conditions.
2002 Semtech Corp.
delay falling edge OUTA rising edge OUTB adaptive triggered when phase node falls below 1.5V. after 220nS phase node still fallen, device will automatically switch. Undervoltage Lockout When supply voltage below undervoltage lockout threshold, both OUTA OUTB held low. COMP also held low. Once undervoltage lockout threshold been surpassed, OUTA, OUTB, COMP released normal operation.
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SC4910A/B
POWER MANAGEMENT Applications Information (Cont.)
Current Sharing ISHARE allows current sharing between several parallel units. ISHARE connects internally non-inverting input ISHARE amplifier. internal resistor between inverting non-inverting inputs this amplifier, with inverting input also connected COMP pin. output amplifier connects (0.75V ref) pin. During normal operation, when devices sharing load current equally, COMP voltages each units should approximately equal. devices begins take much little load, difference COMP voltage will cause ISHARE amplifier adjust (0.75V ref) voltage accordingly. event ISHARE pulled down below ISHARE amplifier disabled prevent output voltage unit lower than specification.
PRELIMINARY
2002 Semtech Corp.
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2002 Semtech Corp.
1.3uH si4842dy 680uF 680uF 680uF 680uF si4842dy 10.0 P8208T si4842dy 1N5819HW ES1D 0.1uF,100V 2.2nF 2.2nF CON2
CON1
+Vin
Vin+
Vout+ Sens
1u,100V
1u,100V
1u,100V
1u,100V
1u,100V
+12V 0.1uF
VinM4 si4842dy
Ishar
0.1uF 1N5819HW SC1301A SC1301A
Sens
+12V
POWER MANAGEMENT Evaluation Board Schematics
1N5819HW 1N5819HW 10.0K si4490dy si4490dy 22nF 37.4k 0.1uF
Vout-
Vref
4.7K SC4431 AVCC PVCC PVCC OUTA DELAY VREF 0.1uF 10.0 -SENSE AGND PGND PGND 47nF COMP 6.19K SC4910 OUTB PHASE 21.5K SYNC/EN ISHARE 20.0K 80.6K 1N5819HW 0.01uF PE68386 0.01uF 150pF 0.1uF 0.1uF 1N5819HW
+12V
18.2k
+12PRI 1N5819HW 1N5819HW
TPS2829
0.1uF
2.2K
0.1uF 80.6K +12PRI 0.47uF 10uF SC4911 150pF 100pF LUVLO COMP 100K 470pF 4.7K 47nF ILIM 130K 1000pF 1.00 100K 2.7MEG 31414R 1N5819HW 47uF +12V 47uF 47uF 100K 1N5819HW +Vin 1N5819HW 383K Si2320DS
SC4910A/B
PRELIMINARY
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SC4910A/B
POWER MANAGEMENT Evaluation Board Bill Materials
Item Quantity Reference CON1 CON2 C1,C32 C3,C4,C5,C33,C34 C6,C7,C8,C9,C10,C35,C51,C52 C11,C12,C14,C15,C16,C17,C22,C36 C13,C29 C18,C19 C21,C30 C23,C24,C25 D2,D5,D6,D7,D9, D10,D11,D12,D20,D21,D22 M1,M2,M3,M4 M5,M6 R2,R26 R3,R37 R4,R6,R17
PRELIMINARY
Part Manufacturer Foot Print
2.2nF 0.1uF,100V (TDK)C3216X7R2A104M 1uF,100V 680uF 0.1uF 150pF 0.01uF 47nF 47uF 0.47uF 10uF 100pF 1000pF 470pF 22nF Diodes Inc. (Murata) GRM55RR72A105KA01B (Sanyo) 4TPB680M
SM/C_0805 SM/C_1206 SM/C_2220 SM/CT_7343 SM/C_0805 SM/C_0805 SM/C_0805 SM/C_0805 SM/C_0805 SM/CT_7343 SM/C_1206 SM/C_1210 SM/C_0805 SM/C_0805 SM/C_0805 SM/C_0805 SM/_SMA SOD123 PCC-S1 SO-8 SO-8 SM/SOT23_123 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805
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1N5819HW Diodes Inc. 0.7uH 2320D "(Panasonic) ETQPAF0R7E" Vishay Vishay Vishay
2002 Semtech Corp.
SC4910A/B
POWER MANAGEMENT Evaluation Board Bill Materials
Item Quantity Reference R11,R35 R21,R25 R27,R30,R33 R50,R51 U1,U2
PRELIMINARY
Part 4.7K 10.0K 37.4K 18.2K 21.5K 2.2K 80.6K 20.0K 6.19K 100K 2.7MEG 383K 130K PA0168 8208T 68386 31414R 1301A 4431 TPS2829 4910 SC4911 Pulse Pulse Pulse Midcom Semtech Semtech "(Texas Instruments) TPS2829DBVR" Semtech Semtech SOT23_5PIN SOT23_5PIN SOT23_5PIN TSSOP-20 MSOP-8
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Manufacturer
Foot Print SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805 SM/R_0805
8208 68386
2002 Semtech Corp.
SC4910A/B
POWER MANAGEMENT Outline Drawing TSSOP-20 PRELIMINARY
Contact Information
Semtech Corporation Power Management Products Division .lynn Road, Camarillo, 93012 Phone: (805)498-2111 (805)498-3804
2002 Semtech Corp.
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PRELIMINARY .eatures Synchronous rectification with adaptive cont

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