General Description
The MAX1515 constant-off-time, pulse-width-modulated
(PWM) source/sink step-down DC-DC converter is opti-
mized for use in low-voltage active-termination power
rails or chipset power supplies in notebook and sub-
notebook computers. This device features dual internal
n-channel MOSFET power switches for high efficiency
and reduced component count. External Schottky
diodes are not required. An integrated boost switch
eliminates the need for an external boost diode. The
internal 40m
Ω
NMOS power switches easily source and
sink continuous load currents up to 3A. The MAX1515
produces an adjustable output from +0.5V to +2.7V
and achieves efficiencies as high as 95%.
The MAX1515 can be configured as a DDR regulator,
producing an output that is exactly half the memory
supply rail. The input of the power stage can be taken
from the memory supply rail itself, resulting in an effi-
cient power supply that returns the energy to the rail
from which it was sourced. The MAX1515 includes a
reference buffer that provides ±5mA of drive current.
The MAX1515 uses a unique current-mode, constant-
off-time, PWM control scheme. A selectable pulse-skip-
ping mode maintains high efficiency during light-load
operation, yet still sources and sinks current on
demand. The MAX1515 can also be operated in fixed-
PWM mode for low output ripple. The programmable
constant-off-time architecture sets switching frequen-
cies up to 1MHz, which allows the user to optimize per-
formance trade-offs between efficiency, output
switching noise, component size, and cost. The
MAX1515 features an adjustable soft-start to limit surge
currents during startup and a low-power shutdown
mode to disconnect the input from the output and
reduce supply current below 1μA. The MAX1515 is
available in a 24-pin thin QFN package with an
exposed backside pad.
Applications
Notebook DDR Memory Termination
Active-Termination Buses
Chipset/Graphics Processor Supplies
Features
Dual 40m
Ω
Internal n-Channel MOSFETs
Integrated Boost Switch
+1.3V to +3.6V Input Voltage Range
1% V
OUT
Accuracy Over Line and Load
1MHz Maximum Switching Frequency
DDR Termination Regulator (DDR Mode)
Tracking Output Voltage
Source/Sink Pulse Skipping
±5mA Reference Buffer
Output Voltage (Non-DDR Mode)
+2.5V, +1.8V, or +1.5V Pin Selectable
+0.5V to +2.7V Adjustable
1.1V ±0.75% Reference Output
Adjustable Soft-Start Inrush Current Limiting
< 1μA (typ) Shutdown Supply Current
< 800μA (max) Operating Supply Current
Selectable Pulse-Skipping Operation at Light Loads
Positive and Negative Current Limit
Power-Good Window Comparator
Output Short-Circuit Protection
Ordering Information
M
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX1515
LX
GND
V
CC
FB
COMP
PGND
IN
REFOUT
PGOOD
V
(3.0V TO 3.6V)
V
(1.3V TO 3.6V)
V
OUT
= V
TT
V
REFOUT
= V
TTR
V
(2.5V OR 1.8V)
MODE
SKIP
FBSEL1
BST
V
DD
SHDN
FBSEL0
SS
REFIN
REF
TOFF
Minimal Operating Circuit
19-3507; Rev 1; 3/06
EVALUATION KIT
AVAILABLE
PART
TEMP RANGE
PIN-
PACKAGE
24 Thin QFN
4mm x 4mm
24 Thin QFN
4mm x 4mm
PKG CODE
MAX1515ETG
-40°C to +85°C
T2444-4
MAX1515ETG+
-40°C to +85°C
T2444-4
Pin Configuration appears at end of data sheet.
+
Denotes lead-free package.