April 1997
PRELIMINARY
ML4901
High Current Synchronous Buck Controller
GENERAL DESCRIPTION
The ML4901 high current synchronous buck controller has
been designed to provide high efficiency DC/DC
conversion for next generation processors such as the
Pentium
®
Pro from Intel
®
.
The ML4901 controller, when combined with 2 external
MOSFETs, generates output voltages between 2.1V and
3.5V from a 12V supply. The output voltage is selected via
an internal 4-bit DAC. Output currents in excess of 14A
can be attained at efficiencies greater than 90%.
The ML4901 can be enabled/disabled via the
SHDN
pin.
While disabled, the output of the regulator is completely
isolated from the circuit’s input supply. The ML4901
employs fixed-frequency PWM control combined with a
dual mode control loop to provide excellent load transient
response.
FEATURES
s
Designed to meet Pentium
®
Pro power supply
requirements
DC regulation to +1% maximum
Proprietary circuitry provides transient response of +5%
maximum over 300mA to 14A load range
Programmable output voltage (2.1V to 3.5V) is set by an
onboard 4-bit DAC
Synchronous buck topology for maximum power
conversion efficiency
Fixed frequency operation for easier system integration
Integrated antishoot-through logic, short circuit
protection, and UV lockout
Shutdown control provides load isolation
s
s
s
s
s
s
s
BLOCK DIAGRAM
(Pin Configuration Shown for 16-Pin SOIC Version)
15
VDD
+
10.4V
PROTECT
16
–
UVLO
+
–
P DRV
14
4.4V
CONTROL
LOGIC
N DRV
13
35µA
+
–
PWR GND
12
SHDN
5
COMP
200kHz
+
–
11
D0
1
VFB
VDAC
-95mV
ISENSE
9
D1
2
D2
3
+
–
10
D3
4
PWR GOOD
6
4 BIT DAC
VDAC
+
–
VDAC + 10%
VDAC + 3%
VFB
VDAC - 10%
VDAC - 3%
8
+
–
VDAC + 3%
VFB
VDAC - 3%
+
–
+
–
3.5V
REFERENCE
GND
VREF
7
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
