DEMO MANUAL DC2315A
LTC4235-1/LTC4235-2
Dual 12V Ideal Diode-OR and Single
Hot Swap Controller with Current Monitor
DESCRIPTION
Demonstration circuit 2315A is intended to demonstrate
the performance of the
LTC
®
4235-1/LTC4235-2
Dual 12V
Ideal Diode-OR and Single Hot Swap™ Controller with
Current Monitor. The controller operates in redundant
12V supply circuits, where each rail has an individual
ideal diode, and the outputs are connected to the load
through a single Hot Swap circuit. The controller enables
monitoring of the load current by providing a signal that
is 100× the sense resistor voltage.
The DC2315A allows verification of the LTC4235 Hot Swap
and ideal diode functionality during individual rail ramp-up
and ramp-down events, during power supply switchover,
in steady state, and in overcurrent fault conditions.
The DC2315A is configured for 12V operation with a 9.0A
maximum current load.
The main board components are the LTC4235 controller,
two power MOSFETs functioning as ideal diodes and one
power MOSFET controlled as a Hot Swap switch, two
jumpers for enabling the second ideal diode (DIODE2_OFF)
and Hot Swap (ON_SEL), two LEDs to indicate power good
(PWRGD) and fault (FAULT) conditions, seven banana
jacks for connecting power supplies and load, and many
turrets and pads for observing circuit signals.
Table 1. DC2315A Assembly Options
VERSION
DC2315A-A
DC2315A-B
PART
LTC4235-1
LTC4235-2
OVERCURRENT FAULT
LATCHOFF
RETRY
Design files for this circuit board are available at
http://www.linear.com/demo/DC2315A
L,
LT, LTC, LTM, Linear Technology, and the Linear logo are registered trademarks and
Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
PERFORMANCE SUMMARY
SYMBOL
Supplies
V
IN
I
LIM
V
INTVCC
V
INTVCC(UVL)
∆V
FWD(REG)
∆V
DGATE
I
CPO(UP)
I
DGATE(FPU)
I
DGATE(FPD)
I
DGATE2(DN)
t
ON(DGATE)
t
OFF(DGATE)
t
PLH(DGATE2)
Input Supply Range
Board Current Limit
Internal Regulator Voltage
Internal V
CC
Undervoltage Lockout
PARAMETER
Specifications are at T
A
= 25°C
CONDITIONS
MIN
9
OUT = 11V
OUT = 0V
INTV
CC
Rising
8
2.3
4.5
2.1
2
∆V
FWD
= 0.15V, I = 0, –1μA
CPO = IN = 12V
∆V
FWD
= 0.2V, ∆V
DGATE
= 0V, CPO = 17V
∆V
FWD
= –0.2V, ∆V
DGATE
= 5V
D2OFF = 2V, ∆V
DGATE2
= 2.5V
∆V
FWD
=0.2V, C
DGATE
= 10nF
∆V
FWD
= –0.2V, C
DGATE
=10nF
50
10
–50
9
3.3
5
2.2
15
12
–90
–1.5
1.5
100
0.25
0.2
50
200
0.5
0.5
100
TYP
MAX
14.0
11.1
4.3
5.5
2.3
28
14
–120
UNITS
V
A
A
V
V
mV
V
µA
A
A
µA
µs
µs
µs
Ideal Diode Control
Forward Regulation Voltage (V
INn
– V
SENSE
+)
External N-Channel Gate Drive (V
DGATEn
– V
INn
)
CPOn Pull-Up Current
DGATEn Fast Pull-Up Current
DGATEn Fast Pull-Down Current
DGATE2 Off Pull-Down Current
DGATEn Turn-On Delay
DGATEn Turn-Off Delay
D2OFF Low to DGATE2 High
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1
DEMO MANUAL DC2315A
PERFORMANCE SUMMARY
SYMBOL
∆V
SENSE(TH)
V
SENSE
+
(UVL)
∆V
SENSE
+
(HYS)
∆V
HGATE
∆V
HGATE(H)
I
HGATE(UP)
I
HGATE(DN)
I
HGATE(FPD)
V
OUT(PGTH)
Input/Output Pin
V
ON(TH)
V
ON(RESET)
V
D2OFF(H,TH)
V
D2OFF(L,TH)
V
FTMR(H)
I
FTMR(UP)
I
FTMR(DN)
D
RETRY
Current Monitor
∆V
REG
V
IMON(OS)
G
IMON
V
IMON(MIN)
R
IMON(OUT)
Floating Regulator Voltage (V
SENSE
+ – V
SENSE
–)
IMON Input Offset Voltage
IMON Voltage Gain
IMON Minimum Output Voltage
IMON Output Resistance
I
REG
= ±1μA
∆V
SENSE
= 0V
∆V
SENSE
= 20mV and 5mV
∆V
SENSE
= 200μV
∆V
SENSE
= 200μV
15
20
99
100
3.6
4.1
4.6
±150
101
40
27
V
μV
V/V
mV
kΩ
ON Pin Threshold Voltage
ON Pin Fault Reset Threshold Voltage
D2OFF Pin High Threshold Voltage
D2OFF Pin Low Threshold Voltage
FTMR Pin High Threshold Voltage
FTMR Pull-Up Current
FTMR Pull-Down Current
Auto-Retry Duty Cycle
FTMR = 1V, In Fault Mode
FTMR = 2V, No Faults
ON Rising
ON Falling
D2OFF Rising
D2OFF Pin Failing
1.21
0.57
1.21
1.19
1.198
–80
1.3
0.07
1.235
0.6
1.235
1.215
1.235
–100
2
0.15
1.26
0.63
1.26
1.24
1.272
–120
2.7
0.23
V
μA
μA
%
V
V
V
PARAMETER
Current Limit Sense Voltage Threshold
(V
SENSE
+ – V
SENSE
–)
SENSE
+
Undervoltage Lockout
SENSE
+
Undervoltage Lockout Hysteresis
External N-Channel Gate Drive (V
HGATE
– V
OUT
)
External N-Channel Gate High Threshold (V
HGATE
– V
OUT
)
External N-Channel Gate Pull-Up Current
External N-Channel Gate Pull-Down Current
External N-Channel Gate Fast Pull-Down Current
OUT Power Good Threshold
Gate Drive On, H
GATE
= 0V
Gate Drive Off, OUT = 12V,
H
GATE
= OUT + 5V
Fast Turn-Off, OUT = 12V,
H
GATE
= OUT + 5V
OUT Rising
I = 0, –1μA
CONDITIONS
OUT = 11V
OUT = 0V
SENSE
+
Rising
MIN
22.5
5.8
1.8
10
10
3.6
–7
1
100
10.2
TYP
25
8.3
1.9
50
12
4.2
–10
2
200
10.5
MAX
27.5
10.8
2
90
14
4.8
–13
4
350
10.8
UNITS
mV
mV
V
mV
V
V
μA
mA
mA
V
Hot Swap Diode Control
2
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DEMO MANUAL DC2315A
OPERATING PRINCIPLES
The LTC4235 is intended to build a combination of two
diode-OR circuits (for two rails) and a common single
Hot Swap path for inrush current limiting and overcurrent
protection.
The LTC4235 regulates the forward voltage drop across
the ideal diode MOSFET to ensure smooth current transfer
from one supply to the other without oscillation. A fast
ideal diode MOSFET turn-on reduces the load voltage
droop during supply switchover. If the input supply fails
or is shorted, a fast turn-off minimizes reverse current
transients.
The Hot Swap fast acting current limit and internal timed
circuit breaker protect circuit components when a short-
circuit fault occurs.
The Hot Swap section of the LTC4235 has independent
on/off control (ON pin).
Each ideal diode MOSFET is activated from an individual
charge pump source and the second ideal diode has an
additional on/off control (D2OFF pin).
The DC2315A-A (LTC4235-1) features a latchoff circuit
breaker, while the DC2315A-B (LTC4235-2) provides
automatic retry after a fault.
Banana Jacks with Associated Turrets
IN1 (E1, E2):
First rail input.
IN2 (E5, E6):
Second rail input.
GND (E3, E4, E7, E8, E14, E15, E21, E22):
Power and
control ground.
SENSE
+
(E16, E17):
SENSE
+
power node.
OUT (E12, E13):
Circuit output for load connection.
Turrets
ON (E18):
On control input.
EN
(E19):
Enable input.
D2OFF (E20):
Enable ideal diode 2.
PWRGD
(E9):
Power status output.
FAULT
(E10):
Fault status output.
CMON (E11):
Current sense monitoring output.
Jumpers
JP1 (ON_SEL):
ON control signal selection.
JP2 (EN_SEL):
Enable signal selection.
JP3 (DIODE2_OFF):
Diode 2 Off-On control.
JP4 (PPRI_SEL):
Prioritizer function selection.
LEDs
D3:
Indicates power good signal.
D4:
Indicates fault signal.
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DEMO MANUAL DC2315A
QUICK START PROCEDURE
Demonstration circuit 2315A is easy to set up to evalu-
ate the performance of the LTC4235. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below.
The DC2315A test includes independent test of the LTC4235
Hot Swap functionality and ideal diode functionality.
HOT SWAP FUNCTIONALITY TEST
This test is performed with a single rail operation when the
output is provided through two series connected MOSFETs.
One MOSFET functions as an ideal diode and the other as
a Hot Swap circuit switch.
The parameters of the three different transients completely
characterize the Hot Swap circuit performance. These
transients are:
n
n
n
Provide an ON signal at the ON pin by changing the JP1
header position from the OFF position to 12V. Observe
the transient. The output voltage rise time should be in
the range of 8.9ms – 19.7ms. The
PWRGD
green LED
D3 must light. The voltmeter at the CMON turret should
display an absolute value not larger than 15mV. Turn
off the rail using the ON_SEL jumper.
2. Connect a disabled electronic load to the OUT turret
and GND. Turn on the rail and slowly increase the
load current up to the circuit breaker threshold level.
The current limit range should be from 8.0A to 11.1A.
The voltage at the CMON turret should be in the range
from 2.22V to 2.77V. Turn off the rail with the ON_SEL
jumper.
3. Initially short the output with an external wire. Place the
current probe on this wire. Turn on the rail and record
the current shape. The maximum current should be in
the 2.3A to 4.3A range, and the voltage at the CMON
turret should be in the range from 0.57V to 1.09V.
IDEAL DIODE FUNCTIONALITY TEST
In this test, both ideal diodes are active and small varia-
tions in the input voltage forces one ideal diode to be off
and the other ideal diode to be on.
Connect input turrets (IN1 and IN2) of each ideal diode
with independent lab supplies. Adjust each input voltage
to +12V with maximum possible accuracy. Place one
voltmeter between IN1 and IN2 turrets to measure the
difference between the two input voltages. Connect an
electronic load to the output turret. Activate both rail and
keep a load around 9A. Play with the input voltage levels
and check that when the difference between input voltages
exceeds 28mV, only one rail feeds the load.
A Power-Up Without Any Additional Load
A Current Limit Operation After Successful Power-Up
A Power-Up With Shorted Output
1. Initially, install the jumpers in the following positions,
if the first ideal diode is used in the test:
JP1:
ON_SEL in the position OFF
JP2:
EN_SEL in the position EN
JP3:
DIODE2_OFF in the position OFF_EXT
If the second ideal diode is used:
JP1:
ON_SEL in the position OFF
JP2:
EN_SEL in the position EN
JP3:
DIODE2_OFF in the position ON
Connect a +12V power supply to turrets IN1 and GND.
Do not load the output. Place the current probe on the
+12V wire, voltage probes on the OUT turret and a
voltmeter on the CMON and GND turrets.
4
dc2315af
DEMO MANUAL DC2315A
QUICK START PROCEDURE
Figure 1. Proper Measurement Equipment Setup
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