July 2000
ML4900*
High Current Synchronous Buck Controller
GENERAL DESCRIPTION
The ML4900 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 ML4900 controller, when combined with two
N-channel MOSFETs, generates output voltages between
2.1V and 3.5V from a 5V 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 ML4900 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 ML4900
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 N-channel 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
(* Indicates Part is End of Life as of July 1, 2000)
BLOCK DIAGRAM
(Pin Configuration Shown for 16-Pin SOIC Version)
15
VDD
+
10.5V
PROTECT
16
–
UVLO
+
–
N DRV H
14
4.4V
CONTROL
LOGIC
+
N DRV L
13
35µA
4V
–
+
–
PWR GND
12
5
1
SHDN
D0
D1
COMP
200kHz
+
–
11
VFB
VDAC
-73mV
ISENSE
9
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 ]
