ML4810 Datasheet, PDF (1/12 Pages) Micro Linear Corporation – High Frequency Power Supply Controller

May 1997
ML4810*, ML4811**
High Frequency Power Supply Controller
GENERAL DESCRIPTION
The ML4810 and ML4811 High Frequency PWM
Controllers are optimized for use in Switch Mode Power
Supply designs running at frequencies to 1MHz. The
ML4810/11 contain a unique overload protection circuit
which helps to limit stress on the output devices and
reliably performs a soft-start reset. These controllers are
designed to work in either voltage or current mode and
provide for input voltage feed forward.
A 1.1V threshold current limit comparator provides a
cycle-by-cycle current limit. An integrating circuit
“counts” the number of times the 1.1V limit was reached.
A soft-start cycle is initiated if the cycle-by-cycle current
limit is repeatedly activated. A reset delay function is
provided on the ML4811.
These controllers are similar to the UC1825 controller,
however these controllers include many features not
found on the 1825. These features are set in Italics.
FEATURES
s Integrating Soft Start Reset
s High current (2A peak) dual totem pole outputs
s Practical operation to 1MHz (f_OSC)
s 5.1V ±2% trimmed bandgap reference
s Under voltage lockout with 7V hysteresis
s Soft Start Reset Delay (ML4811)
s Oscillator synchronization function (ML4811)
s Soft Start latch ensures full soft start cycle
s Outputs pull low for undervoltage lockout
s Accurately controlled oscillator ramp discharge current
s All timing currents “slaved” to R_T for precise control
* This part is End of Life as of August 1, 2000
** This part is Obsolete
BLOCK DIAGRAM (Pin numbers shown are for ML4811)
6 ^RT
CT
7
OSC
SYNC
10
O.V.P./SHUTDOWN
11
RAMP
8
1.25V
E/A OUT
3
2 ^NI
ERROR
+ ^AMP
1 ^INV
–
9 ^{SOFT START}
2.2V
+
–
COMP
+
I(1)
–
V+
I(1)
CQ
TF.F.
P
Q
1.1V –
+
ILIM/SD
12
+
–
1.5V
2.45V
–
+
S
3× I(1)
RC (RESET)
4
Q
RESET DELAY
20
R
1.1V
+
CLOCK
–
V+
SQ
R
5.1V
1.1V
CLOCK
5
R
SQ
POWER GND
PWR VC ₁₆
OUT A
14
POWER VC
OUT B
17
POWER GND
15
4V
ENABLE
V_REF
VREF GEN
9V
INTERNAL
BIAS
UNDER
VOLTAGE
LOCKOUT
3V
I(1) = _{16 x RT}
1.5V VREF
19
V_{CC 18}
GND
13
1