DEMO CIRCUIT 1329
LTC4352
QUICK START GUIDE
LTC4352
Low Voltage Ideal Diode Controller
with Monitoring
Design files for this circuit board are available.
Call the LTC factory.
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DESCRIPTION
Demonstration circuit 1329 showcases the
LTC4352, a Low Voltage Ideal Diode Controller w/
Monitoring, in a DFN-12 package. The LTC4352
creates a near-ideal diode using external N-
channel MOSFET therby replacing high power
Schottky diode and associated heat sink. Ideal di-
odes enable low loss power ORing and supply
holdup applications.
L
, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are
PERFORMANCE SUMMARY
SYMBOL
V
IN
PARAMETER
Input Operating Range
Specifications are at TA = 25°
C
CONDITIONS
With External 2.9V to 4.7V
V
CC Supply
I
OUT
V
CC(EXT)
V
CC(INT)
V
FWD(REG)
Output Load Current
V
CC
External Supply Range
V
CC
Internal Regulator Voltage
Forward Regulation Voltage (V
IN
– V
OUT
)
With External 4.7V to 6V
V
CC Supply
V
IN
< V
CC
MIN
2.9
0
0
0
2.9
3.4
10
TYP
MAX
18
V
CC
10
6
4.6
40
18
UNITS
V
4.1
25
A
V
V
mV
OPERATING PRINCIPLES
The LTC4352 regulates the forward voltage drop
across the external MOSFET to ensure smooth
current transfer in diode-OR applications. A fast
turn-on reduces the load voltage droop during
supply switch-over. If the input supply fails or is
shorted, a fast turn-off minimizes reverse current.
The controller operates with rail voltages from 2.9v
to 18V. Operation with rail voltages below 2.9V re-
quires additional supply on V
CC
from 2.9V to 6.0V.
Undervoltage and overvoltage protection (not used
in the demo board circuit) allows the controller to
operate in a restricted input voltage range.
The controller features an open MOSFET detect
circuit that flags excessive voltage drop across the
pass transistor in the on state.
The
STATUS
pin signal (green LED) indicates the
MOSFET on state, and the
FAULT
pin signal (red
LED) indicates an undervoltage, overvoltage or
open MOSFET fault.
1
LTC4352
QUICK START PROCEDURE
Demonstration circuit 1329 is easy to set up to
evaluate the performance of the LTC4352. Refer to
Error! Reference source not found.
for proper
measurement equipment setup. The DC1329 in-
cludes two identical but separate circuits. In the
sample test procedure below, each circuit tested
as a single ideal diode (described for top-half cir-
cuit #1) and after that both circuit are tested for
OR-ing operation with a common load.
these pins set the overvoltage and undervolt-
age levels.
7.
Place jumper JP1 in the HIGH position. Ap-
ply 5VVIN1. Measure voltage between VIN1
and VOUT1 turrets with no load. The voltage
should be lower than 1mV. Replace JP1 to
LOW position.
8.
With VIN1=5V apply 10A electronic load be-
tween VOUT1 and GND. Measure VIN1-
VOUT1 voltage, it should be between 40mV
and 60mV.
9.
With VIN1=5V connect a 9V alkaline bat-
tery’s negative terminal to GND and the posi-
tive terminal to VOUT1. The
STATUS
green
LED will turn off, as the circuit is preventing
reverse current from flowing.
Ideal Diode Test
.
1.
Place jumper JP1 (REV1) in the LOW posi-
tion
JP1 (REV1)
LOW
2.
Adjust lab power supply output voltage to
2.9V. Place voltmeters to measure DC1329
input voltage (Vin1), voltage between VIN1
and VOUT1 turrets (Vin1-VOUT1), and VCC1
voltage. Turn switch SW1 on to apply 2.9V to
the board. The
STATUS
green LED should
light.
3.
Increase the input voltage from 2.9V up to
17V and observe that voltage between VIN1
and VOUT1 is the Forward Regulation Volt-
age of 25mV±15mV, the voltage at the VCC1
turret follows closely below the input voltage
from 2.9V up to 4.1V, and regulates to 4.1V
with higher input voltages. The
STATUS
LED
should stay green.
4.
Adjust the board input voltage to +5.0V.
Connect one terminal of a test lead to the
GND turret and other to the UV pin (pin 3).
The
FAULT
red LED should light and
STATUS
green LED goes off.
5.
Connect one terminal of the test lead to the
VIN1 turret and other to the OV pin (pin4).
The
FAULT
red LED should light and
STATUS
green LED goes out.
6.
Note: The UV and OV pin thresholds are
500mV +/-10mV. Appropriate dividers on
Ideal Diode-ORing Test
.
10.
Adjust both supplies’ output voltage to 5V.
Turn both switches SW1 and SW2 on. In the
case when only one ideal-diode is on, slightly
increase the output voltage of the supply op-
erating in the off channel to have both chan-
nels on. If both channels are on, slightly
change the output voltage of one supply to
check that one ideal-diode channel will be off
when difference between input voltages ex-
ceeds difference between forward regulation
voltages (25mV±15mV).
11.
Adjust both supplies output voltage to 5V.
Turn both switches SW1 and SW2 on. Make
both channels on as described in paragraph
11. Apply a common load of 10A. Slightly
change the output voltage of one supply to
check that one ideal-diode channel will be off
when difference between input voltages ex-
ceeds sum of difference between forward
regulation voltages and difference between
voltage drops in the MOSFET and traces.
2
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