LTC4230
1
DESCRIPTION
Demonstration circuit DC537A is designed to
evaluate the performance of the LTC4230 Triple
Hot Swap Controller with multifunction current con-
trol. The board demonstrates all possible operation
modes: power-up and power-down, when power
rails turn on or turn off, steady state with constant
load and overload conditions.
The board contains one LTC4230 Controller, three
power channels, three resistive feedback signal
dividers, an ON pin circuit, and a circuit for con-
figuration of the FAULT pin function. Each power
channel includes a series connected power
MOSFET and sense resistor.
Design files for this circuit board are available.
Call the LTC factory.
LTC is a trademark of Linear Technology Corporation.
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Supply Voltage V
CC1
Supply Voltage V
CC2
Supply Voltage V
CC3
V
CC2
≤
V
CC1
V
CC3
≤
(V
CC1
-1)
2.700
2.375
1.700
16.5
16.5
16.5
V
Undervoltage Lockout, Channel 1 VCC1 Low to High Transition 2.13 2.35 2.52
V
Undervoltage Lockout, Channel 2 VCC2 Low to High Transition 1.98 2.15 2.32
V
Undervoltage Lockout, Channel 3 VCC3 Low to High Transition 1.09 1.19 1.29
V
Circuit Breaker Trip Current Fast Comparator
Slow Comparator
19.1
5.65
21.4
7.14
23.8
8.65 A
GATEn Pin Pull-Up Slew Rate Charge Pump On, 0
≤
V
GATE
≤
0.2V 0.42 0.74 1.13 V/ms
Normal Gate Pull-Down Slew Rate ON Low, GATE=5V 14.70 V/ms
Fast Gate Pull-Down Slew Rate FAULT Latched and Circuit Breaker Tripped
or in UVLO 10.0 V/
µ
s
ON High Threshold Voltage
ON Low Threshold Voltage
ON Low to High Transition
ON High to Low Transition
1.250
1.172
1.314
1.234
1.380
1.27
V
V
FB Low Threshold Voltage FB High to Low Transition 1.209 1.234 1.259
V
FB Hysteresis 3
mV
Supply Voltage VCC1 V
CC2
≤
V
CC1
V
CC3
≤
(V
CC1
-1) 2.700
16.5
V
Supply Voltage VCC2
2.375
16.5
V
Supply Voltage VCC3
1.700
16.5
V
Undervoltage Lockout, Channel 1 VCC1 Low to High Transition 2.13 2.35 2.52
V
Undervoltage Lockout V
IN
Rising, 0°C < T
A
< 85°C
V
IN
Rising
V
IN
Falling
1.6
2.5
2.6
V
DEMO CIRCUIT
537
QUICK START GUIDE
LTC4230
Triple Hot Swap Co
n-
troller with Multifun
c-
LTC4230
2
OPERATING PRINCIPLES
The LTC4230 is a triple hot swap controller that
controls three supply voltages from 1.7V to 16.5V
with V
CC1
V
CC2
V
CC3
.
The LTC4230 is suited to low voltage power con-
trol in applications for hot board insertion or re-
moval and electronic circuit breaker functions. The
LTC4230 provides a rich set of features to support
Hot Swap applications including:
■
Under voltage lockout
■
Programmable over voltage protection
■
Programmable soft start with inrush current limit-
ing
■
Dual level over current fault protection
■
Programmable over current response time
■
Automatic retry or latched mode operation
■
User-programmable supply voltage power-up
rate
■
Output voltages V
OUTn
monitoring and RESETn
signaling
■
Spurious RESETn signal elimination by the
glitch filter
Available in a 20 lead SSOP package, the
LTC4230 is showcased on demonstration circuit
DC537A configured for 1.7 to 16.5 volt operation
with a slow comparator current limit protection in
the range of 5.71A - 8.57A and a fast comparator –
in the range of 19.3A - 23.6A.
Pull-up resistors are provided to monitor the RE-
SETn pin signals.
MOSFET gate capacitors C7, C8, C9 define the
output voltage slew rate. Initially the board is popu-
lated for nominal 0.74V/ms slew rate in each
power channel.
The external ON control signal should be higher
than 2.8V.
Three optional Zener diodes (D4, D5, and D6) can
be used to protect the system against supply over-
voltage condition on the load side of the pass
transistor.
QUICK START PROCEDURE
Demonstration circuit 537 is easy to set up to
evaluate the performance of the LTC4230. Refer to
Figure 1 for proper board connections with power
supplies, loads, and the ON control signal source.
Demonstration Circuit 537 has three optional
components R13, R10, and R7 for the output
voltage monitoring value adjustments and one
user configurable jumper JP1 option.
Calculate R13, R10, and R7 resistors based at the
selected channel voltages and install them on the
board.
Place jumper J1 in the AUTORETRY position to
evaluate automatic retry when current limit is
reached, or in the STATUS position to evaluate
latched mode operation.
With power off, connect three power supplies ca-
pable of supplying 25A to the appropriate V1_IN,
V2_IN, V3_IN turrets and GND. Supplies voltages
should satisfy the conditions shown in the
PERFORMANCE SUMMARY and V
CC1
•
V
CC2
;
V
CC3
•
(V
CC1
-1).
Connect the ON pin to a signal source capable of
developing 16V>VON>1.39V to the turret labeled
ON/OFF and be sure that the ON signal is initially
zero (low).
NO LOAD TEST
Turn on the power supplies, verify the input volt-
ages, and then switch the ON control signal from
low to high (1.39V).
All three outputs should come up.
LTC4230
3
Verify the RESETn turret signals. All three voltages
should be lower than 0.5V.
Switch the ON control signal from high to low. All
outputs should go down.
RATED LOAD TEST
Repeat the test with resistive loads connected to
each output. Be sure that the current in each chan-
nel does not exceed 5.65A current limit.
OVER CURRENT FAULT TEST
Three separate tests are needed to verify the cir-
cuit breaker functions. First two tests run with con-
ditions for slow comparator operation; third test –
for fast comparator operation. Monitor the turn off
events with a digital storage scope.
1.
With the outputs unloaded and the circuit func-
tioning, connect a load to the selected channel
output, which will draw 10A current.
The channel will fault. Verify latch off and auto-
matic retry modes by changing the jumper JP1
position.
Repeat this test for each channel.
2.
With the jumper JP1 in the STATUS position, the
board unpowered and the ON control signal
high, connect a load capable of drawing 10A to
any channel output. Leave the other two chan-
nels unloaded.
First, turn the two unloaded channel supplies
on. Then turn on the third supply and verify that
LTC4230 is in the latch mode.
NOTE.
This test can be run only with the components initially
installed on the board and the channel operating voltage
V
CCn
•
12V. Otherwise, the MOSFET can operate out of the safe
operating area, and not survive. Higher operating voltages or
higher currents require a larger FET.
3.
Adjust the resistive load to draw 24A current in
channel 1 to demonstrate the FAST comparator
fault..
With the jumper JP1 in the STATUS position, the
unloaded outputs and the circuit functioning,
connect this load to the channel 1 output.
Verify that LTC4230 is in the latch mode.
UNDER VOLTAGE LOCKOUT TEST
Test under voltage lockout functionality by reduc-
ing the input voltage below 2.15V for channel 1,
below 1.98V for channel 2, and below 1.09V for
channel 3.
CHANNEL SEQUENCING
If power on sequencing is desired, remove the
RESETn pin pull-ups. Choose the channel se-
quence in the power up mode. Connect the RE-
SETn1 pin to the GATEn2 pin; connect RESETn2
pin to the GATEn3 pin. The additional indexes 1, 2,
3 show channel sequencing order. As FBn1 pin
exceeds its threshold RESETn1 will release the
MOSFET GATEn2 pin; as the FBn2 pin exceeds
its threshold, RESETn2 will release the channel
MOSFET GATEn3 pin.
Apply ON signal and observe the start up se-
quencing.
LTC4230
4
LTC4230
5
