Linear Technology DC1555A Demo Manual page 2

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
QUICK START PROCEDURE
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
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
tive, but it will be clamped by the internal protection
diode.)
7) Ramp supply back to 0V.
2
and GND in negative
IN
slightly nega-
OUT
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 to GND (connect positive rail to V
IN
rail to GND).
9) Ramp supply up to 30V and verify green V
FAULT LED, green V
OUT
Table 1 within the various voltage ranges.
10) Ramp supply down from 30V down to 0V and verify
LED, red FAULT LED, green V
green V
IN
V according to Table 1.
OUT
11) Repeat steps 9 and 10 with 8A load connected across
V and GND.
OUT
Table 1
V V
IN OUT
0V to 5.77V = 0V
6.56V to 13.51V = V
IN
15.47V to 30V = 0V
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
EN CONNECT LED
DIS CONNECT LED
EN Open
and negative
IN
LED, red
IN
LED, and V according to
OUT
LED, and
OUT
FAULT LED
V LED V LED
IN OUT
Off/Dim/On Off On
On On Off
On Off On
VIN LED VOUT LED
On On
On Off
Off Off
dc1555af