Owner's manual
MAX1947
Detailed Description
The MAX1947 compact step-up DC-DC converter starts
up with voltages as low as 0.8V and operates with input
voltages down to 0.7V. An internal synchronous rectifier
reduces cost by eliminating the need for an external
Schottky diode and improves overall efficiency by
reducing losses in the circuit. The efficiency is further
increased with the low 70µA quiescent current and low
on-resistance of the internal n-channel MOSFET power
switch. The MAX1947 uses Maxim’s proprietary True
Shutdown circuitry, which disconnects the output from
the input in shutdown and actively discharges the
output to ground.
Low Input/Output Voltage
Step-Up DC-DC Converter with
RESET
6 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 RESET
Active-Low Push-Pull Reset Output. RESET goes high 75ms (min) after the output voltage has
exceeded 90% of its final value. The RESET output is valid for output voltages as low as 0.9V. RESET
is driven low in shutdown.
2 GND Ground. Connect to exposed paddle.
3 GND Ground. Connect to exposed paddle.
4 SHDN
Shutdown Input. Connect to BATT or logic 1 for normal operation. Connect to GND or logic 0 for a low
quiescent-current shutdown mode.
5 PGND Power Ground. Connect to exposed paddle.
6LX
Inductor Connection to the Drains of the Internal N-Channel Switch and P-Channel Synchronous
Rectifier
7 OUT
Regulator Output. Bypass with 10µF ceramic capacitor to GND for full-load capability. For less than
50% of full load, a 4.7µF capacitor can be used.
8 BATT Batter y C onnecti on. V
B A TT
i s used for the star tup osci l l ator and to p ow er the chi p w hen V
OU T
< V
B A TT
.
—EPExposed Paddle. Connect to GND and PGND.
POWER-ON RESET WAVEFORMS
MAX1947toc17
V
IN
V
OUT
V
RESET
1V/div
1V/div
1V/div
20ms/div
EXITING AND ENTERING
SHUTDOWN WAVEFORMS
MAX1947toc18
V
OUT
V
SHDN
V
RESET
1V/div
1V/div
1V/div
20ms/div
Typical Operating Characteristics (continued)
(V
IN
= 1.5V, Circuit of Typical Application Circuit, T
A
= +25°C, unless otherwise noted.)