1
dc826cf
DEMO MANUAL
DC826C-A/DC826C-B
DESCRIPTION
LTC2950-2/LTC2951-2
Pushbutton On/Off Controller
Demonstration circuits 826C-A and 826C-B feature the
LTC
®
2950-2
and the
LTC2951-2
respectively, which are
low power, wide input voltage range, pushbutton on/off
controllers. A pushbutton switch shorts the
PB
pin to
ground which in turn sets the
EN
pin low (see Note 1).
Shorting
PB
to ground a second time subsequently resets
the
EN
pin high. The
EN
pin is used to connect to a DC/
DC converter shutdown to control the turn on and off of
the circuit, simulated with a green LED on the DC826C-A/
DC826C-B.
JP1 and JP2 on the DC826C-A provide the selection
of timing options for the
PB
on and off times. For the
DC826C-B, JP1 selects
KILL
times while JP2 selects off
L
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Technology Corporation. All other trademarks are the property of their respective owners.
IC SELECTION GUIDE
times. JP3 ties and unties
KILL
to
INT
for immediate or
delayed turn off. The
INT
status is shown with a red LED.
DC826C-A/DC826C-B accepts an input voltage range of
2.7V to 26.4V or a 9V battery for portable demonstration
and evaluation.
Note 1
: The inversion of
EN
of the LTC2950-2/LTC2951-2
is found in the LTC2950-1/LTC2951-1. Table 1 provides
an IC selection guide.
Design files for this circuit board are available at
http://www.linear.com/demo/DC826C
Table 1. LTC2950/LTC2951 Selection Guide (Typical Timing Values, Cap. Adjust = 212ms on DC826C-A/DC826C-B)
PART
ENABLE ONT
OFFT
KILLT
DEMO BOARD
LTC2950-1
EN
32ms + Cap. Adjust*
32ms + Cap. Adjust*
1000ms
N/A
LTC2950-2
EN
32ms + Cap. Adjust*
32ms + Cap. Adjust*
1000ms
DC826C-A
LTC2951-1
EN
128ms
32ms + Cap. Adjust*
128ms + Cap. Adjust*
N/A
LTC2951-2
EN
128ms
32ms + Cap. Adjust*
128ms + Cap. Adjust*
DC826C-B
*The additional Cap. Adjust time is selected by an external capacitor. The DC826C-A and DC826C-B adjust times have been pre-selected with a 0.033μF
capacitor to provide an additional 212ms. The additional time is calculated with the following equations as shown in the LTC2950/LTC2951 data sheets:
C
ONT
= 1.56e-4 [μF/ms] • (t
ONT
– 1ms)
C
OFFT
= 1.56e-4 [μF/ms] • (t
OFFT
– 1ms)
C
KILLT
= 1.56e-4 [μF/ms] • (t
KILL
,
OFF DELAY, ADDITIONAL
– 1ms)
