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DEMO MANUAL DC1555B
operAting principles
The LTC4365 monitors the input rail voltage and discon-
nects downstream circuits when the input voltage is too
low, too high or negative. The LTC4365 provides accurate
overvoltage and undervoltage comparators to ensure that
power is applied to the system only if the input supply
is within the allowable voltage window. Reverse supply
qUick stArt proceDUre
Demonstration circuit 1555B is easy to set up to evaluate
the performance of the LTC4365. Refer to Figures 1a and
1b for proper measurement equipment setup and follow
the procedure below.
Note that the circuit on the DC1555B is optimized for 12V
operation; The Si4230 FET limits overvoltage and reverse
voltage to 30V and –30V, respectively. Refer to the LTC4365
data sheet for applications optimized for other voltages.
Reverse Voltage Tests (Figure 1a)
1) Set JP1 to EN.
2) Set JP2 and JP3 to CONNECT LED.
3) Connect a power supply across V
configuration (connect positive rail to GND and negative
rail to V
).
IN
4) Connect voltmeters at the input and output and ammeter
in series with supply.
5) Ramp supply down to –30V (referenced to GND).
6) Verify output voltage is between 0V and –0.5V, all LEDs
are off, and input current is <1.8mA. (FET leakage or
other board leakage paths can pull V
tive, but it will be clamped by the internal protection
diode.)
7) Ramp supply back to 0V.
2
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protection circuit automatically isolates the load from
negative input voltages.
During normal operation, a high voltage charge pump
enhances the gate of external N-channel power MOSFETs.
The LTC4365 consumes 10µA during shutdown and 125µA
while operating.
Undervoltage/Overvoltage Test (Figure 1b)
8) Reverse the polarity of power supply connection across
9) Ramp supply up to 30V and verify green V
10) Ramp supply down from 30V down to 0V and verify
11) Repeat steps 9 and 10 with 8A load connected across
and GND in negative
IN
Table 1
Jumper Test
12) Remove load and set supply to 9V.
slightly nega-
OUT
13) Move jumpers and verify LEDs according to Table 2.
Table 2
V
to GND (connect positive rail to V
IN
rail to GND).
FAULT LED, green V
OUT
Table 1 within the various voltage ranges.
green V
LED, red FAULT LED, green V
IN
V
according to Table 1.
OUT
V
and GND.
OUT
V
V
IN
OUT
0V to 5.77V
= 0V
Off/Dim/On
6.56V to 13.51V
= V
IN
15.47V to 30V
= 0V
JP1
JP2/JP3
EN
CONNECT LED
DIS
CONNECT LED
EN
Open
and negative
IN
LED, red
IN
LED, and V
according to
OUT
LED, and
OUT
V
LED
V
LED
FAULT LED
IN
OUT
Off
On
On
On
Off
On
Off
On
VIN LED
VOUT LED
On
On
On
Off
Off
Off
dc1555bfa
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