5V/12V/15V or Adjustable, High-Efficiency,
Low I
Q
, Step-Up DC-DC Controllers
MAX770–MAX773
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 2a, T
A
= +25°C, unless otherwise noted.)
MAX770
EXITING SHUTDOWN
A
0
B
0
200µs/div
V
IN
= 3V, I
OUT
= 0.5A
A: SHDN, 2V/div
B: V
OUT
, 2V/div
______________________________________________________________Pin Description
PIN
MAX770
MAX771
MAX772
1
2
3
4
5
6
7
8
—
—
—
—
—
MAX773
—
3
6
7
8
—
9
11
1
2
4
5
10
NAME
FUNCTION
EXT
V+
FB
SHDN
REF
AGND
GND
CS
V12
V5
LBO
LBI
SGND
Gate drive for external N-channel power transistor
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.
Analog ground
High-current ground return for the output driver
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.
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.
Input to the internal low-battery comparator. Tie to GND or V+ if not used.
Shunt regulator ground. Leave unconnected if the shunt regulator is
not
used.
_______________________________________________________________________________________
7
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
