Datasheet
MAX770–MAX773
5V/12V/15V or Adjustable, High-Efficiency,
Low I
Q
, Step-Up DC-DC Controllers
_______________________________________________________________________________________
7
V
IN
= 3V, I
OUT
= 0.5A
A: SHDN, 2V/div
B: V
OUT
, 2V/div
MAX770
EXITING SHUTDOWN
A
B
0
0
200µs/div
______________________________________________________________Pin Description
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, T
A
= +25°C, unless otherwise noted.)
PIN
NAME FUNCTION
MAX773
1 — EXT Gate drive for external N-channel power transistor
2 3 V+
3 6 FB
4 7 SHDN
5 8 REF
6 — AGND Analog ground
7 9 GND High-current ground return for the output driver
8 11 CS
— 1 V12
— 2 V5
MAX770
MAX771
MAX772
Power-supply input. Also acts as a voltage-sense point when in bootstrapped mode for the
MAX770/MAX771/MAX772, or as a shunt regulator when SGND is connected to ground for the
MAX773. Bypass to SGND with 0.1µF when using the shunt regulator.
Feedback input for adjustable-output operation. Connect to ground for fixed-output operation. Use
a resistor divider network to adjust the output voltage. See
Setting the Output Voltage
section.
Active-high TTL/CMOS logic-level shutdown input. In shutdown mode, V
OUT
is a diode drop
below V+ (due to the DC path from V+ to the output) and the supply current drops to 5µA
maximum. Connect to ground for normal operation.
1.5V reference output that can source 100µA for external loads. Bypass to GND with 0.1µF.
The reference is disabled in shutdown.
Positive input to the current-sense amplifier. Connect the current-sense resistor between CS and GND.
Input sense point for 12V-output operation. Connect V
OUT
to V12 for 12V-output operation.
Leave unconnected for adjustable-output operation.
Input sense point for 5V-output operation. Connect V
OUT
to V5 for 5V-output operation. Leave
unconnected for adjustable-output operation.
— 4 LBO
— 5 LBI Input to the internal low-battery comparator. Tie to GND or V+ if not used.
— 10 SGND
Shunt regulator ground. Leave unconnected if the shunt regulator is not used.
Low-battery output is an open-drain output that goes low when LBI is less than 1.5V. Connect to V+
through a pull-up resistor. Leave floating if not used. LBO is high impedance in shutdown mode.