Datasheet

LTC6655
13
6655fd
For more information www.linear.com/LTC6655
C
OUT
= 3.3µF
6655 F08
1ms/DIV
V
OUT
1V/DIV
SHDN
2V/DIV
C
OUT
= 3.3µF
6655 F07
200µs/DIV
2mA
–2mA
I
OUT
V
OUT
10mV/DIV
applicaTions inForMaTion
Figure 8. Shutdown Response with 5mA Source Load
LTC6655-2.5
V
IN
GND
SHDN
2N7002
V
OUT_F
V
OUT_S
TO µC
3V ≤ V
IN
≤ 13.2V
V
OUT
C1
1µF
C2
10µF
6655 F09
Figure 9. Open-Drain Shutdown Circuit
Figure 7. Output Response Showing a
Sinking to Sourcing Transition
shutdown due to system noise or leakage currents. The
turn-on/turn-off response due to shutdown is shown in
Figure 8.
To control shutdown from a low voltage source, a MOSFET
can be used as a pull-down device as shown in Figure 9.
Note that an external resistor is unnecessary. A MOSFET
with a low drain-to-source leakage over the operating
temperature range should be chosen to avoid inadvertently
pulling down the SHDN pin. A resistor may be added from
SHDN to V
IN
to overcome excessive MOSFET leakage.
The SHDN thresholds have some dependency on V
IN
and temperature as shown in the Typical Performance
Characteristics section. Avoid leaving SHDN at a voltage
between the thresholds as this will cause an increase in
supply current due to shoot-through current.
0mA
–5mA
I
OUT
V
OUT
10mV/DIV
C
OUT
= 3.3µF
6655 F05
200µs/DIV
5mA
0mA
I
OUT
V
OUT
10mV/DIV
C
OUT
= 3.3µF
6655 F06
200µs/DIV
Figure 6. Output Response with 5mA Load Step Sinking
Figure 5. Output Response with a 5mA Load Step Sourcing
Long-Term Drift
Long-term drift cannot be extrapolated from accelerated
high temperature testing. This erroneous technique gives
drift numbers that are wildly optimistic. The only way
long-term drift can be determined is to measure it over
the time interval of interest.
The LTC6655 long-term drift data was collected on 80 parts
that were soldered into printed circuit boards similar to a
real world application. The boards were then placed into a
constant temperature oven with a T
A
= 35°C, their outputs
were scanned regularly and measured with an 8.5 digit
DVM. Typical long-term drift is illustrated in Figure 10a.
The hermetic LS8 package provides additional stability as
shown in Figure 10b.