SI9124 Datasheet, PDF (2/16 Pages) Vishay Siliconix – 500-kHz Push-Pull DC-DC Converter With Integrated Secondary Synchronous Rectification Control

Si9124
Vishay Siliconix
New Product
DESCRIPTION (CONTINUED)
Si9124 has advanced current monitoring circuitry to permit the
user to set the maximum current in the primary circuit. Such a
feature acts as protection against output shorts. Upon sensing
an overload condition, the converter is shut off for a period of
time and then soft-start cycle is re-initiated, achieving hiccup
mode operation. Current sensing is by means of a sense
resistor on the primary device. An integrated over-temperature
shutdown circuit also protects the system.
The 100-V depletion mode MOSFET integrated pre-regulator
circuit permits direct operation from input voltage with only one
series resistor during startup. The pre-regulator automatically
disconnects from the input supply when the output voltage is
established by means of a feedback winding from the filter
inductor.
Si9124 is available in TSSOP-16 pin package. In order to
satisfy the stringent ambient temperature requirements,
Si9124 is rated to handle the industrial temperature range of
–40 to 85_C.
DETAILED BLOCK DIAGRAM
V_IN
Pre-Regulator
V_CC
+ ^VUVLO
-
8.8 V
V_REF
R_OSC
V_INDET
V_REF
Error Amplifier
2.2 R
R
EP
-
+
1.65 V
SS
Gain
CS2
+
CS1
-
+ ^VUV
-
+ ^VSD
-
550 mV
PWM
+ ^Comparator
-
I
4I
Peak DET
Hiccup
Mode Start
V_FF
Ramp
OSC
Driver
Control
and
Timing
OTP
Over Current Protection
GND
Level
Shift
Primary A
Driver
V_CC2
OUT_A
PGND₂
V_CC
Primary B
Driver
OUT_B
V_CC
SEC_SYNC
SEC_SYNC
Driver
Si9124
PGND
Figure 2.
www.vishay.com
2
Document Number: 72099
S-03638—Rev. B, 20-Mar-03