Datasheet

LTC6652
12
6652fe
For more information www.linear.com/6652
applications inForMation
Figure 8. Start-Up Response without Output Capacitor
Figure 9. Start-Up Response with 1µF Output Capacitor
Figure 10. Open-Drain Shutdown Circuit
Figure 11. Shutdown Response with 5mA Load
In Figure 8, ripple momentarily appears just after the
leading edge of powering on. This brief one time event is
caused by calibration circuitry during initialization. When
an output capacitor is used, the ripple is virtually undetect-
able as shown in Figure 9.
Shutdown Mode
Shutdown mode is enabled by tying SHDN low which
places the part in a low power state (i.e., <2µA). In shut-
down mode, the output pin takes the value 20k • (rated
output voltage). For example, an LTC6652-2.5 will have
an output impedance of 20k • 2.5 = 50kΩ. For normal
operation, SHDN should be greater than or equal to 2.0V.
For use with a microcontroller, use a pull-up resistor to
V
IN
and an open-drain output driver as shown in Figure
10. The LTC6652’s response into and out of shutdown
mode is shown in Figure 11.
The trip thresholds on SHDN have some dependence on the
voltage applied to V
IN
as shown in the Typical Performance
Characteristics section. Be careful to avoid leaving SHDN
at a voltage between the thresholds as this will likely cause
an increase in supply current due to shoot-through current.
V
IN
2V/DIV
V
OUT
1V/DIV
100µs/DIV
6652 F08
C
OUT
= 0µF
2.8V ≤ V
IN
≤ 13.2V
V
OUT
TO µC
C1
1µF
C2
1µF
R1
20k
6652 F10
LTC6652-2.5
SHDN
2N7002
V
OUT
V
IN
GND
V
IN
2V/DIV
V
OUT
1V/DIV
100µs/DIV
6652 F09
C
OUT
= 1µF
SHDN
1V/DIV
V
OUT
1V/DIV
1ms/DIV
6652 F11
I
LOAD
= 5mA