SI9122 Vishay Siliconix, SI9122 Datasheet - Page 2

• Manufacturer Part Number: SI9122
• Description: 500-kHz Half-Bridge DC-DC Converter With Integrated Secondary Synchronous Rectification Drivers
• Manufacturer: Vishay Siliconix

Si9122
Vishay Siliconix
TECHNICAL DESCRIPTION
Si9122 is a voltage mode controller for the half-bridge
topology. With 100-V depletion mode MOSFET capability, the
Si9122 is capable of powering directly from the high voltage
bus to V
powered through an external regulator directly through the
V
throughout the entire line and load range. In order to simplify
the traditional secondary synchronous rectification, Si9122
provides 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 a source rating of the MOSFETs. Si9122 provides constant
V
charge loss as well as conduction loss. A break-before-make
function is included to prevent shoot through current or
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2
DETAILED BLOCK DIAGRAM
CC
GS
pin. With PWM control, Si9122 provides peak efficiency
voltage, independent of line voltage to minimize the gate
REG_COMP
CC
V
INDET
V
through an external PNP pass transistor, or may be
CS2
CS1
REF
EP
SS
20 mA
Error Amplifier
60 kW
Pre-Regulator
I
SS
V
V
Over Current Protection
IN
REF
8 V
132 kW
+
−
V REF
−
+
GND
2
V
CC
9.1 V
Peak DET
8.8 V
+
−
+
−
+
−
550 mV
Comparator
+
−
V
V
V
UVLO
PWM
UV
SD
Figure 2.
Duty Cycle
C
Control
L_CONT
transformer shorting. Adjustable Break-Before-Make time is
incorporated into the IC and is programmable by an external
resistor value.
Si9122 is packaged in
In TSSOP-20 packaging, both standard and lead (Pb)-free
options
lead (Pb)-free.
temperature requirements, Si9122 is rated to handle the
industrial temperature range of –40 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 the current loop. Monitoring of the load current is
by means of a sense resistor on the primary low-side switch.
V
FF
Ramp
BBM
are
Control
Timing
Driver
R
OSC
and
OSC
OTP
available.
In order to satisfy the stringent ambient
High-Side
Primary
Driver
TSSOP-20 and MLP65-20
Si9122
Low-Side
Driver
The
Int
MLP65-20
SYNC
Driver High
SYNC
Driver Low
S-41944—Rev. F, 18-Oct-04
V
V
V
Document Number: 71815
CC
CC
CC
package
BST
D
L
D
PGND
SR
SR
X
H
L
packages.
H
L
is