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dc1555af
DEMO MANUAL DC1555A
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
Demonstration circuit 1555A 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 DC1555A 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
IN
and GND in negative
confi guration (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
OUT
slightly nega-
tive, but it will be clamped by the internal protection
diode.)
7) Ramp supply back to 0V.
QUICK START PROCEDURE
protection circuits 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
V
IN
to GND (connect positive rail to V
IN
and negative
rail to GND).
9) Ramp supply up to 30V and verify green V
IN
LED, red
FAULT
LED, green V
OUT
LED, and V
OUT
according to
Table 1 within the various voltage ranges.
10) Ramp supply down from 30V down to 0V and verify
green V
IN
LED, red
FAULT
LED, green V
OUT
LED, and
V
OUT
according to Table 1.
11) Repeat steps 9 and 10 with 8A load connected across
V
OUT
and GND.
Table 1
V
IN
V
OUT
V
IN
LED
V
OUT
LED
FAULT
LED
0V to 5.77V
= 0V
Off/Dim/On
Off
On
6.56V to 13.51V
= V
IN
On
On
Off
15.47V to 30V
= 0V
On
Off
On
Jumper Test
12) Remove load and set supply to 9V.
13) Move jumpers and verify LEDs according to Table 2.
Table 2
JP1
JP2/JP3
VIN LED
VOUT LED
EN
CONNECT LED
On
On
DIS
CONNECT LED
On
Off
EN
Open
Off
Off
