SC4806 Datasheet, PDF (1/22 Pages) Semtech Corporation – Multiple Function Double Ended PWM Controller

POWER MANAGEMENT
Description
The SC4806 is a double ended, high speed, highly
integrated PWM controller optimized for applications
requiring minimum space. The device is easily configurable
for current mode or voltage mode operation and contains
all the control circuitry required for isolated applications,
where a secondary side error amplifier is used.
Designed for simplicity, the SC4806 is fully featured and
requires only a few external components. It features a
programmable frequency up to 1MHZ, external
programmable soft start, pulse-by-pulse current limit and
over current protection for both voltage and current
modes, as well as a line monitoring input with hysteresis
to reduce stress on the power components. A ramp pin
allows for slope compensation to be programmed by
external resistors for current mode. This also allows for
operation in voltage mode with voltage feed forward.
A unique oscillator is utilized which allows two SC4806
to be synchronized together and work out-of-phase. This
feature minimizes the input and output ripples, and
reduces stress and size on input/output filter components.
The outputs are configured for push-pull format, dead time
between the 2 outputs is programmable depending on the
size of the timing components.
The SC4806 features a turn on threshold of 8 volts .
The device is available at a MLP-12 package.
Typical Application Circuit
SC4806
Multiple Function
Double Ended PWM Controller
Features
‹ 90 µA starting current
‹ Pulse-by-pulse current limit for both voltage/current
modes
‹ Programmable operating frequency up to 1MHz
‹ Programmable external soft start
‹ Programmable line undervoltage lockout
‹ Programmable external slope compensation
‹ Over current shutdown with separate pin
‹ Dual output drive stages on push-pull configuration
‹ Programmable mode of operation (peak current mode
or voltage mode)
‹ External frequency synchronization
‹ Bi-phase mode of operation
‹ Lead free MLP-12 package,WEEE and RoHS
compliant
‹ -40 to 105 °C operating temperature
Applications
‹ Telecom equipment and power supplies
‹ Networking power supplies
‹ Industrial power supplies
‹ Push-pull converter
‹ Half bridge converter
‹ Full bridge converter
‹ Isolated VRMs
+VIN
-VIN
ON/OFF
REF
+
SYNC
4 _RC
5 _ILIM
6 _RAMP
I sense
Vcc
SC4806
Vcc
VCC ¹²
OUTA ¹¹
OUTB ¹⁰
Rsense
SC1301A
SC1301A
+
REF
FB
SC431
+Vo
-Vo
Revision: October 13, 2006
REF
FB
I sense
1
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