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SI9124 Datasheet(Fiches technique) 8 Page - Vishay Siliconix

Numéro de pièce SI9124
Description  500-kHz Push-Pull DC-DC Converter With Integrated Secondary Synchronous Rectification Control
Télécharger  16 Pages
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Fabricant  VISHAY [Vishay Siliconix]
Site Internet  http://www.vishay.com
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SI9124 Datasheet(HTML) 8 Page - Vishay Siliconix

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Si9124
Vishay Siliconix
New Product
www.vishay.com
8
Document Number: 72099
S-03638—Rev. B, 20-Mar-03
DETAILED FUNCTIONAL BLOCK DIAGRAM
Figure 5.
+
-
132 k
W
EP
+
-
-
+
-
+
VREG
9.1 V
VCC
VIN
Pre-Regulator
VUVLO
8.6 V
Reference
Voltage
3.3 V
Voltage
Feedforward
OSC
160
_C Temp
Protection
VSD VUV VUVLO
Logic
Clock
OTP
VREF
VINDET
-
+
ROSC
Oscillator
Clock
60 k
W
VREF/2
PWM
Generator
-
+
-
+
VUV
VSD
VREF
550 mV
Logic
OUTA
VCC2
PGND2
Primary A
Driver
OUTB
SEC_SYNC
PGND
Primary B
Driver
Secondary
Synchronous
Driver
GND
Current
Control
Gain
100 mV
CS2
CS1
VCC
VCC
Blanking
SS Enable
VCC
20
mA
80
mA
SS Control
SS
VREF
9.1 V
DETAILED OPERATION
Start-Up
A detailed Functional Block Diagram is shown in Figure 5 with
additional detail of the pre-regulator shown in Figure 6. The
pre-regulator circuit acts as a linear regulator to provide VCC
directly from the VINEXT supply until the VCC supply voltage
between 10 V to 13.2 V can be sustained from an auxiliary
winding from the secondary of the power inductor.
When VINEXT rises above 0 V (see Figure 6), the internal
pre-regulator begins charging the external capacitor on VCC.
The charging current is limited to typically 40 mA by the internal
DMOS device. When Vcc exceeds the UVLO voltage of 8.8 V,
a soft-start cycle of the controller is initiated to provide power
to the secondary. Once switching commences, the internal
gate drivers for the primary side switching transistors and the
drive current into the secondary synchronization driver draw
additional current from the VCC capacitor and pre-regulator.


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