LTC2956_15 Datasheet, PDF (20/26 Pages) Linear Technology – Wake-Up Timer with Pushbutton Control

LTC2956
Applications Information
C1
100nF
+
R20
10k
PB
V_IN
LTC2956
GND
LOAD
2956 F16a
Figure 16a. PMOS Reverse Battery Protection
Interface with Switching Regulators
The LTC2956-1 EN pin can be connected directly to most
switching regulator SHUTDOWN inputs. The EN pin high
level output voltage (V_EN(V_OH)) is typically 3.3V when
V_IN > 3.5V, and V_EN(V_OH) = V_IN – 0.1V if V_IN <3.0V. With
a minimum V_IN of 1.5V, V_EN(OH) is still higher than most
SHUTDOWN thresholds. Figure 17 shows one such ap-
plication. The LTC3528 regulator is a boost converter
with a SHUTDOWN high threshold of 0.88V (maximum).
+
R20
10k
C1
100nF
PB
V_IN
LTC2956
GND
LOAD
2956 F16b
Figure 16b. NMOS Reverse Battery Protection
If a higher V_EN(V_OH) is required, an external pull-up
resistor can be connected from the EN pin to any higher
voltage (<36V). The EN pin is designed to be able to sink
at least 1mA of current during turn-off, so this external
pull-up resistor value must be selected to source less
than 1mA with EN at 0V. The LTC2956-1 EN pin can also
be connected to switching regulators with a RUN/SS pin.
RUN/SS typically has a dual function of a SHUTDOWN
threshold and soft-start. Switching regulators optimized for
4.7µH
V_IN
1.5V TO 3.2V
4.7µF
PB ^VIN
EN
C_ONMAX
GND
ONMAX
R_PERIOD
PERIOD
PBOUT
LTC2956-1 ONALERT
OFFALERT
SLEEP
LONG RANGE
SW
LTC3528
V_IN
V_OUT
499k
PGOOD
FB
SHDN
287k
GND
R_LONG 100k
R_RANGE
Figure 17. 2-Cell with 3.3V Output
22pF
V_OUT
3.3V, 0.4A
22µF
2956 F17
2956f
20
For more information www.linear.com/LTC2956