19-0305; Rev 3; 3/09
KIT
ATION
EVALU
ABLE
AVAIL
5V/3.3V or Adjustable, High-Efficiency,
Low-Dropout, Step-Down DC-DC Controllers
The MAX1649/MAX1651 BiCMOS, step-down, DC-DC
switching controllers provide high efficiency over loads
ranging from 1mA to more than 2.5A. A unique, currentlimited pulse-frequency-modulated (PFM) control scheme
gives these devices the benefits of pulse-width-modulation (PWM) converters (high efficiency at heavy loads),
while using only 100µA of supply current (vs. 2mA to
10mA for PWM converters). Dropout performance down
to 300mV is provided by a high switch duty cycle (96.5%)
and a low current-sense threshold (110mV).
A high switching frequency (up to 300kHz) allows these
devices to use miniature external components.
The MAX1649/MAX1651 have dropout voltages less
than 0.3V at 500mA and accept input voltages up to
16V. Output voltages are preset at 5V (MAX1649), or
3.3V (MAX1651). They can also be adjusted to any
voltage from 1.5V to the input voltage by using two
resistors.
____________________________Features
♦ More than 90% Efficiency (10mA to 1.5A Loads)
♦ More than 12.5W Output Power
♦ Less than 0.3V Dropout Voltage at 500mA
♦
♦
♦
♦
100µA Max Quiescent Supply Current
5µA Max Shutdown Supply Current
16V Max Input Voltage
5V (MAX1649), 3.3V (MAX1651), or Adjustable
Output Voltage
♦ Current-Limited Control Scheme
♦ Up to 300kHz Switching Frequency
♦ Up to 96.5% Duty Cycle
______________Ordering Information
________________________Applications
PDAs
High-Efficiency Step-Down Regulation
5V-to-3.3V Green PC Applications
Battery-Powered Applications
TEMP RANGE
0°C to +70°C
8 Plastic DIP
MAX1649CSA
MAX1649C/D
MAX1649EPA
MAX1649ESA
MAX1651CPA
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
8 SO
Dice*
8 Plastic DIP
8 SO
8 Plastic DIP
MAX1651CSA
MAX1651C/D
MAX1651EPA
MAX1651ESA
These step-down controllers drive external P-channel
MOSFETs at loads greater than 12.5W. If less power is
required, use the MAX639/MAX640/MAX653 step-down
converters with on-chip FETs, which allow up to a
225mA load current.
PART
MAX1649CPA
PIN-PACKAGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
8 SO
Dice*
8 Plastic DIP
8 SO
*Dice are tested at TA = +25°C.
__________Typical Operating Circuit
INPUT
3.6V TO 16V
__________________Pin Configuration
TOP VIEW
V+
OUT
ON/OFF
SHDN
CS
EXT
OUT
REF
FB
GND
P
1
8
GND
FB
MAX1651
2
7
EXT
6
CS
5
V+
SHDN 3
OUTPUT
3.3V
MAX1649
MAX1651
REF 4
DIP/SO
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
1
MAX1649/MAX1651
_______________General Description
