SI9122E Datasheet, PDF (2/20 Pages) Vishay Siliconix – 500-kHz Half-Bridge DC/DC Controller with Integrated Secondary Synchronous Rectification Drivers

Si9122E
Vishay Siliconix
TECHNICAL DESCRIPTION
Si9122E is a voltage mode controller for the half-bridge
topology. With 100 V depletion mode MOSFET, the Si9122E
is capable of powering directly from the high voltage bus to
V_CC through an external PNP pass transistor, or may be
powered through an external regulator directly through the
V_CC pin. With PWM control, Si9122E provides peak
efficiency throughout the entire line and load range. In order
to simplify the design of efficient secondary synchronous
rectification circuitry, the Si9122E 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 source
rating of the secondary-side MOSFETs. Si9122E provides
constant V_GS voltage, independent of the line voltage to
minimize the gate charge loss as well as conduction loss.
To prevent shoot-through current or transformer shorting,
adjustable Break-Before-Make (BBM) time is incorporated
into the IC and is programmed by an external precision
resistor.
Si9122E is assembled in lead (Pb)-free TSSOP-20 and
MLP65-20 packages. To satisfy stringent ambient
temperature requirements, Si9122E 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. With the lower
OTP set at 135 °C , the DNF20 package improves the
thermal headroom.
V_IN
V_CC
R_OSC
REG_COMP
V_INDET
V_REF
EP
SS
CS2
CS1
Pre-Regulator
V_REF
9.1 V
+
V_UVLO
-
8.8 V
+ ^VUV
-
132 k
+ ^VSD
-
60 k
Error Amplifier
20 µA
I_SS
–
+
V _REF
2
550 mV
+
–
PWM
Comparator
8V
Over Current Protection
High-Side
Primary
Driver
Int
V_FF
Ramp
OSC
Low-Side
Primary
Driver
Driver
Control
and
Timing
OTP
+
–
Peak DET
Duty Cycle
Control
Si9122E
GND
C_{L_CONT}
BBM
Figure 2.
BST
DH
LX
V_CC
DL
PGND
V_CC
SR_H
SYNC
Driver High
V_CC
SR_L
SYNC
Driver Low
ABSOLUTE MAXIMUM RATINGS All voltages referenced to GND = 0 V
Parameter
Limit
Unit
V_IN (Continuous)
V_IN (100 ms)
V_CC
V_BST
Continuous
100 ms
80
100
14.5
95
113.2
V_LX
V_BST - V_LX
V_REF, R_OSC
Logic Inputs
Analog Inputs
HV Pre-Regulator Input Current
Continuous
100
V
15
- 0.3 to V_CC + 0.3
- 0.3 to V_CC + 0.3
- 0.3 to V_CC + 0.3
5
mA
www.vishay.com
2
Document Number: 73866
S-80112-Rev. D, 21-Jan-08