SC4910A Datasheet, PDF (1/19 Pages) Semtech Corporation – High Performance Secondary Side Controller with Synchronous Rectifier

SC4910A/B
High Performance Secondary Side
Controller with Synchronous Rectifier
POWER MANAGEMENT
Description
The SC4910A/B is an integrated, full featured, second-
ary side controller designed for use in single ended and
isolated switch mode power supplies with synchronous
rectification where efficiency and fast transient response
are of primary concern. The SC4910A/B has outputs for
both primary FET and secondary synchronous rectifica-
tion. The primary drive output is designed to drive a small
and low cost pulse transformer to isolate the primary
FET driver. The secondary control makes it much easier
to monitor and control the system load with tight control
loops and implement load current sharing and synchro-
nous rectification.
The SC4910A/B features synchronous rectification, multi-
phase link capability, programmable secondary side
delay, programmable switching frequency and program-
mable maximum duty cycle. It is designed for either
current mode or voltage mode operation.
The SC4910A has a typical turn-on threshold of 9V and
the SC4910B has a threshold of 4.5V.
Typical Application Circuit
Features
‹ Synchronous rectification with adaptive control
‹ Programmable secondary side delay
‹ Programmable switching frequency
‹ Programmable max. duty cycle
‹ Remote voltage sense capability
‹ Close-loop soft start with active low shutdown
‹ 0.75V precision reference for low output applications
‹ Oscillator sychronization
‹ Undervoltage Lockout
‹ Operation to 1MHz
‹ Current-mode or voltage-mode operation
‹ Single stage power conversion with multiphase link
capability (with SC4201)
‹ Monotonic start-up with pre-biased output
‹ Active current sharing capability
‹ 20 pin TSSOP package
Applications
‹ Telecom isolated DC to DC converters
‹ Isolated VRMS
‹ Networking power supplies
‹ Industrial power supplies
‹ Distributed power architectures
‹ High density power modules
+Vin
T1
R2
C3
C1
D1
L1
M1
M2
R1
C2
LOAD
SC1301
SC1301
+12V
SC1301
M3
C4
12
SC4910
13
14
T2
D2
4
PVCC
CS
PVCC
AVCC ₁₆
ISHARE
R3
10
OUTA
PHASE ⁶
R4
20 _RT1
R5
19 _RT2
3 _SS
OUTB ¹¹
C5
COMP ¹⁷
FB ¹⁸
C6
R6
R7
15 _DELAY
2
SYNC/EN
5
VREF
-SENSE ¹
R8
AGND PGND PGND
C9
T3
C10
7
C8 _R9
8
9
D3
Revision: June 1, 2005
1
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