MAX1644EAE-T Datasheet, PDF (1/11 Pages) Maxim Integrated Products – 2A, Low-Voltage, Step-Down Regulator with Synchronous Rectification and Internal Switches

19-1457; Rev 3; 8/05
EVAALVUAAILTAIOBNLEKIT
2A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
General Description
The MAX1644 constant-off-time, PWM step-down DC-
DC converter is ideal for use in applications such as PC
cards, CPU daughter cards, and desktop computer
bus-termination boards. The device features internal
synchronous rectification for high efficiency and
reduced component count. It requires no external
Schottky diode. The internal 0.10Ω PMOS power switch
and 0.10Ω NMOS synchronous-rectifier switch easily
deliver continuous load currents up to 2A. The
MAX1644 produces a preset +3.3V or +2.5V output
voltage or an adjustable output from +1.1V to V_IN. It
achieves efficiencies as high as 95%.
The MAX1644 uses a unique current-mode, constant-
off-time, PWM control scheme, which includes an Idle
Mode™ to maintain high efficiency during light-load
operation. The programmable constant-off-time archi-
tecture sets switching frequencies up to 350kHz, allow-
ing the user to optimize performance trade-offs
between efficiency, output switching noise, component
size, and cost. The device also features an adjustable
soft-start to limit surge currents during start-up, a 100%
duty cycle mode for low-dropout operation, and a low-
power shutdown mode that disconnects the input from
the output and reduces supply current below 1µA. The
MAX1644 is available in a 16-pin SSOP package.
Applications
+5V to +3.3V/+2.5V Conversion
CPU I/O Supply
+3.3V PC Card and CardBus Applications
Notebook and Subnotebook Computers
Desktop Bus-Termination Boards
CPU Daughter Card Supply
Typical Operating Circuit
INPUT
+3V TO
+5.5V
R_TOFF
IN
LX
MAX1644 FB
V_CC
FBSEL
SHDN
COMP
TOFF
PGND
GND
REF
SS
OUTPUT
+1.1V TO
V_IN
Features
♦ ±1% Output Accuracy
♦ 95% Efficiency
♦ Internal PMOS and NMOS Switches
70mΩ On-Resistance at V_IN = +4.5V
100mΩ On-Resistance at V_IN = +3V
♦ Output Voltage
+3.3V or +2.5V Pin-Selectable
+1.1V to V_IN Adjustable
♦ +3V to +5.5V Input Voltage Range
♦ 360µA (max) Operating Supply Current
♦ < 1µA Shutdown Supply Current
♦ Programmable Constant-Off-Time Operation
♦ 350kHz (max) Switching Frequency
♦ Idle Mode Operation at Light Loads
♦ Thermal Shutdown
♦ Adjustable Soft-Start Inrush Current Limiting
♦ 100% Duty Cycle During Low-Dropout Operation
♦ Output Short-Circuit Protection
♦ 16-Pin SSOP Package
Ordering Information
PART
TEMP RANGE
MAX1644EAE
40°C to +85°C
MAX1644EAE+
40°C to +85°C
+Denotes lead-free package.
PIN-PACKAGE
16 SSOP
16 SSOP
Pin Configuration
TOP VIEW
SHDN 1
IN 2
LX 3
IN 4
SS 5
COMP 6
TOFF 7
FB 8
MAX1644
SSOP
16 LX
15 PGND
14 LX
13 PGND
12 V_CC
11 FBSEL
10 REF
9 GND
Idle Mode is a trademark of Maxim Integrated Products, Inc.
A "+" SIGN WILL REPLACE THE FIRST PIN INDICATOR ON LEAD-FREE PACKAGES.
________________________________________________________________ Maxim Integrated Products 1
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.