MAX1515 Datasheet, PDF (1/24 Pages) Maxim Integrated Products – Low-Voltage, Internal Switch, Step-Down/DDR Regulator

19-3507; Rev 1; 3/06
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Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
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 40mΩ 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
Pin Configuration appears at end of data sheet.
Features
♦ Dual 40mΩ 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
PART
TEMP RANGE
PIN-
PACKAGE
PKG CODE
MAX1515ETG -40°C to +85°C ^{24 Thin QFN} T2444-4
4mm x 4mm
MAX1515ETG+ -40°C to +85°C ^{24 Thin QFN} T2444-4
4mm x 4mm
+Denotes lead-free package.
Minimal Operating Circuit
VBIAS
(3.0V TO 3.6V)
VDDQ
(2.5V OR 1.8V)
VDD
BST _IN
VCC
MAX1515
COMP
LX
PGOOD
FB
SHDN
PGND
MODE
SKIP
REF
GND
FBSEL0
FBSEL1
REFIN
REFOUT
SS
TOFF
VIN
(1.3V TO 3.6V)
VOUT = VTT
VREFOUT = VTTR
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