SI9122A_08 VISHAY [Vishay Siliconix], SI9122A_08 Datasheet - Page 2

• Manufacturer Part Number: SI9122A_08
• Description: 500-kHz Half-Bridge DC/DC Controller with Integrated Secondary Synchronous Rectification Drivers
• Manufacturer: VISHAY [Vishay Siliconix]

Si9122A
Vishay Siliconix
TECHNICAL DESCRIPTION
Si9122A is a voltage mode controller for the half-bridge
topology. With 100 V depletion mode MOSFET capability,
the Si9122A is capable of powering directly from the high
voltage bus to V
or may be powered through an external regulator directly
through the V
peak efficiency throughout the entire line and load range. In
order to simplify the design of efficient secondary
synchronous
intelligent gate drive signals to control the secondary
MOSFETs. With independent gate drive signals from the
controller, transformer design is no longer limited by the gate
to source rating of the secondary-side MOSFETs. Si9122A
provides constant V
to minimize the gate charge loss as well as conduction loss.
SI9122 BLOCK DIAGRAM
www.vishay.com
2
REG_COMP
V
CC
INDET
V
rectification
CS2
CS1
CC
REF
EP
SS
pin. With PWM control, Si9122A provides
through an external PNP pass transistor,
GS
20 µA
voltage, independent of line voltage
Error Amplifier
circuitry,
60 kΩ
Pre-Regulator
I
SS
V
V
Over Current Protection
IN
REF
8 V
132 kΩ
Si9122A
+
-
V REF
-
+
GND
2
V
CC
9.1 V
Peak DET
provides
8.8 V
+
-
+
-
+
-
550 mV
Comparator
+
-
V
V
V
UVLO
PWM
Figure 2.
UV
SD
Duty Cycle
C
Control
A break-before-make function is included to prevent shoot
through current or transformer shorting. Adjustable Break-
Before-Make time is incorporated into the IC and is
programmable by an external resistor value.
Si9122A is packaged in lead (Pb)-free TSSOP-20 and
MLP65-20
temperature requirements, Si9122A is rated to handle the
industrial temperature range of - 40 °C to 85 °C. When a
situation arises which results in a rapid increase in primary
(or secondary current) such as output shorted or start-up
with a large output capacitor, control of the PWM generator
is handed over to the current loop. Monitoring of the load
current is by means of an external current sense resistor in
the source of the primary low-side switch.
L_CONT
V
FF
Ramp
BBM
packages.
Control
Timing
Driver
R
OSC
and
OSC
OTP
High-Side
Primary
Driver
To
Si9122
Low-Side
Driver
satisfy
Int
S-80038-Rev. D, 14-Jan-08
Document Number: 73492
stringent
SYNC
Driver High
SYNC
Driver Low
V
V
V
CC
CC
CC
ambient
BST
D
L
D
PGND
SR
SR
X
H
L
H
L