ML4828 Datasheet, PDF (1/11 Pages) Micro Linear Corporation – BiCMOS Phase Modulation/Soft Switching Controller

May 1997
ML4828*
BiCMOS Phase Modulation/Soft Switching Controller
GENERAL DESCRIPTION
The ML4828 is a complete BiCMOS phase modulation
control IC suitable for full bridge soft switching converters.
Unlike conventional PWM circuits, the phase modulation
technique allows for zero voltage switching (ZVS)
transitions and square wave drive across the transformer.
The IC modulates the phases of the two sides of the bridge
to control output power.
The ML4828 can be operated in either voltage or current
mode. Both cycle-by-cycle current limit, integrating fault
detection, and soft start reset are provided. The under-
voltage lockout circuit features a 1.5V hysteresis with a
low starting current to allow off-line start up with a bleed
resistor. A shutdown function powers down the IC, putting
it into a low quiescent state.
The circuit can be operated at frequencies up to 1MHz.
The ML4828 contains four high current CMOS outputs
which feature high slew rate with low cross conduction.
FEATURES
s 5V BiCMOS for low power and high frequency
(1MHz) operation
s Full bridge phase modulation zero voltage switching
circuit with independent programmable delay times
s Current or voltage mode operation capability
s Cycle-by-cycle current limiting with integrating fault
detection and restart delay
s Can be externally synchronized
s Four 3Ω CMOS output drivers
s Under-voltage lockout circuit with 1.5V hysteresis
*Some Packages Are End Of Life
BLOCK DIAGRAM
VCC
14
SDN 19
UVLO
EA+ 10 +
EA– 9 –
ERROR
AMP
EAO 8
RAMP 11
SS 7
2.5V ₊
1.25V
–
VREF
5
2.5V REF
SYNC RT CT
63 4
OSC
ISS
ΦMOD
–
+
Q
S
Q
R
Q
T
Q
RST 12
ILIM 20
1V
ILIM
+
–
IRST
FAULT
LOGIC
R
Q
S
Q
17
GND
DRIVER
18 A1
DELAY A
DRIVER 16 A2
DRIVER 15 ^B1
DELAY B
DRIVER 13 B2
1
2
R_A
RB
1