SI9124 Datasheet, PDF (1/16 Pages) Vishay Siliconix – 500-kHz Push-Pull DC-DC Converter With Integrated Secondary Synchronous Rectification Control

New Product
Si9124
Vishay Siliconix
500-kHz Push-Pull DC-DC Converter With
Integrated Secondary Synchronous Rectification Control
FEATURES
D 12-V to 72-V Input Voltage Range
D Compatible with ETSI 300 132-2 100 V, 100-ms
Transients
D Integrated Push-Pull 1-A Primary Drivers
D Voltage Mode Control
D Voltage Feedforward Compensation
D High Voltage Pre-Regulator Operates During Start-Up
D Current Sensing On OUT_B Primary Device
D Hiccup Current Control During Shorted Load
D Low Input Voltage Detection
D Programmable Soft-Start Function
D Programmable Oscillator Frequency
D Over Temperature Protection
APPLICATIONS
D Network Cards
D Power Supply Modules
DESCRIPTION
Si9124 is a dedicated push-pull controller IC ideally suited to
fixed telecom dc-dc converter applications where high
efficiency is required at low output voltages (e.g. <3.3 V).
Designed to operate within the voltage range of 12-72 V and
withstand 100 V, 100 ms transients, the IC is capable of
controlling and directly driving both primary side MOSFET
switches of a push-pull circuit.
High conversion efficiency is achieved by use of synchronous
rectifying MOSFET transistors in the secondary. Due to the
very low on-resistance of the secondary MOSFETs, a
significant increase in the efficiency can be achieved as
compared with conventional Schottky diodes for today’s low
output voltages. On-chip control of the dead time delays
between the primary and secondary signals keep efficiencies
high and prevents accidental destruction of the power
transformer or wasted energy from self timed approaches.
Such a system can achieve conversion efficiencies well in
excess of 90%.
FUNCTIONAL BLOCK DIAGRAM
V_INEXT
V_CC
CV_CC
EP
Voltage
Information
SS
C_SS
CS2
CS1
R_EXT
V_IN
Pre-Reg
Voltage
Control
Soft-
Start
PWM
Current
Control
Si9124
Push-Pull
Synchronous
Controller
+
- ^CVIN1
Primary
Drivers
OUT_A
Power
Transformer
Secondary
Driver
OUT_B
R_S
SEC_SYNC
Pulse
Transformer
Driver
Logic
To
V_CC
C_LOAD
V_OUT
R_LOAD
Figure 1.
Opto
Error
Amp
1.215 V
Document Number: 72099
S-03638—Rev. B, 20-Mar-03
www.vishay.com
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