applications that allows a board to be safely inserted and
removed from a live backplane. The part integrates a
Hot Swap controller, power MOSFET and current sense
resistor in a single package for small form factor applica-
tions. The MOSFET Safe Operating Area is production tested
and guaranteed for the stresses in Hot Swap applications.
The LTC4234 provides separate inrush current control
and an 11% accurate 22.5A current limit with output
dependent foldback. The current limit threshold can be
adjusted dynamically using the I
SET
pin. Additional features
include a current monitor output that amplifies the sense
resistor voltage for ground referenced current sensing
and a MOSFET temperature monitor output. Thermal limit,
overvoltage, undervoltage and power good monitoring are
also provided. For a 10A compatible version, see LTC4233.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
Hot Swap and PowerPath are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
Allows Safe Board Insertion into Live Backplane
Small Footprint
4mΩ MOSFET Including R
SENSE
Safe Operating Area Guaranteed at 81W, 30ms
Wide Operating Voltage Range: 2.9V to 15V
Adjustable, 11% Accurate Current Limit
Current and Temperature Monitor Outputs
Overtemperature Protection
Adjustable Current Limit Timer Before Fault
Power Good and Fault Outputs
Adjustable Inrush Current Control
2.5% Accurate Undervoltage and Overvoltage Protection
Pin Compatible with LTC4233
Available in a 38-Pin (5mm
×
9mm) QFN Package
APPLICATIONS
n
n
n
n
High Availability Servers
Solid State Drives
Industrial
240W, 12V Systems
TYPICAL APPLICATION
12V, 20A Card Resident Application with Auto-Retry
12V
*
107k
V
DD
UV
FLT
5.23k
OV
10k
SENSE
–
SENSE
TIMER
1µF
*TVS: DIODES INC. SMAJ17A
INTV
CC
GND
LTC4234
PG
GATE
I
SET
I
MON
20k
ADC
4234 TA01a
OUT
150k
FB
20k
+
10k
1000µF
V
OUT
12V
20A
V
IN
10V/DIV
I
IN
0.2A/DIV
V
OUT
10V/DIV
PG
10V/DIV
Power-Up Waveform
CONTACT
BOUNCE
20ms/DIV
4234 TA01b
4234fa
For more information
www.linear.com/LTC4234
1
LTC4234
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
PIN CONFIGURATION
TOP VIEW
UV 1
OV 2
I
MON
3
TIMER 4
INTV
CC
5
V
DD
(DNC) 6
GND 7
SENSE (DNC) 8
OUT 9
OUT 10
OUT 11
OUT 12
OUT 13
OUT 14
OUT 15
OUT 16
17
OUT
18
OUT
19
OUT
20
OUT
21
OUT
22
OUT
40
SENSE
39
V
DD
38 I
SET
37 FB
36
FLT
35 PG
34 SENSE
–
33 V
DD
(DNC)
32 GATE
31 SENSE
30 OUT
29 OUT
28 OUT
27 OUT
26 OUT
25 OUT
24 OUT
23 OUT
Supply Voltage (V
DD
) ................................. –0.3V to 28V
Input Voltages
FB, OV, UV ..............................................–0.3V to 12V
TIMER ................................................... –0.3V to 3.5V
SENSE
−
, SENSE .....V
DD
− 10V or –0.3V to V
DD
+ 0.3V
Output Voltages
I
SET
, I
MON
................................................. –0.3V to 3V
PG,
FLT
................................................. –0.3V to 35V
OUT ............................................ –0.3V to V
DD
+ 0.3V
INTV
CC
.................................................. –0.3V to 3.5V
GATE (Note 3) ........................................ –0.3V to 33V
Operating Ambient Temperature Range
LTC4234C ................................................ 0°C to 70°C
LTC4234I .............................................–40°C to 85°C
LTC4234H .......................................... –40°C to 125°C
Junction Temperature (Notes 4, 5)........................ 150°C
Storage Temperature Range .................. –65°C to 150°C
WHH PACKAGE
38-LEAD (5mm
×
9mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 15°C/W
EXPOSED PADS (PINS 39 and 40) ARE V
DD
AND SENSE
θ
JA
= 15°C/W SOLDERED, OTHERWISE
θ
JA
= 50°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC4234CWHH#PBF
LTC4234IWHH#PBF
LTC4234HWHH#PBF
TAPE AND REEL
LTC4234CWHH#TRPBF
LTC4234IWHH#TRPBF
LTC4234HWHH#TRPBF
PART MARKING
4234
4234
4234
PACKAGE DESCRIPTION
38-Lead (5mm
×
9mm) Plastic QFN
38-Lead (5mm
×
9mm) Plastic QFN
38-Lead (5mm
×
9mm) Plastic QFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
4234fa
2
For more information
www.linear.com/LTC4234
LTC4234
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DD
= 12V unless otherwise noted.
SYMBOL
PARAMETER
DC Characteristics
Input Supply Range
V
DD
Input Supply Current
I
DD
Input Supply Undervoltage Lockout
V
DD(UVL)
OUT Leakage Current
I
OUT
dV
GATE
/dt
R
ON
I
LIM(TH)
SOA
Inputs
I
IN
I
SENSE
−
(IN)
V
TH
∆V
OV(HYST)
∆V
UV(HYST)
V
UV(RTH)
∆V
FB(HYST)
R
ISET
Outputs
V
INTVCC
V
OL
I
OH
V
TIMER(H)
V
TIMER(L)
I
TIMER(UP)
I
TIMER(DN)
I
TIMER(RATIO)
A
IMON
BW
IMON
I
OFF(IMON)
I
GATE(UP)
I
GATE(DN)
I
GATE(FST)
OUT Turn-On Ramp Rate
MOSFET + Sense Resistor On-Resistance
Current Limit Threshold
MOSFET Safe Operating Area
CONDITIONS
l
ELECTRICAL CHARACTERISTICS
MIN
2.9
2.63
1
0.15
2.3
2.3
20
4
9.4
30
7
TYP
MAX
15
3
2.85
±700
4
0.6
7.2
8.2
25
7.4
12.8
UNITS
V
mA
V
µA
µA
V/ms
mΩ
mΩ
A
A
A
ms
ms
µA
µA
V
mV
mV
V
mV
kΩ
V
V
µA
V
V
µA
µA
%
µA/A
kHz
µA
µA
µA
mA
MOSFET On, No Load
V
DD
Rising
V
OUT
= V
GATE
= 0V, V
DD
= 15V
V
OUT
= V
GATE
= 12V
GATE Open
C-Grade, I-Grade
H-Grade
V
FB
= 1.35V, I
SET
Open
V
FB
= 0V, I
SET
Open
V
FB
= 1.35V, R
SET
= 20k
13.5V, 6A Folded Back, 200W
2
s (Note 6)
7.5V, 22A Onset of Foldback, 200W
2
s (Note 7)
V = 1.2V
V
SENSE−
= 12V
V
PIN
Rising
l
l
l
l
l
l
l
l
l
l
1.6
2.73
0
2
0.35
4.0
4.0
22.5
5.7
11.1
OV, UV, FB Input Current
SENSE
−
Input Current
OV, UV, FB Threshold Voltage
OV Hysteresis
UV Hysteresis
UV Reset Threshold Voltage
FB Power Good Hysteresis
I
SET
Internal Resistor
INTV
CC
Output Voltage
PG,
FLT
Output Low Voltage
PG ,
FLT
Input Leakage Current
TIMER High Threshold
TIMER Low Threshold
TIMER Pull-Up Current
TIMER Pull-Down Current
TIMER Current Ratio I
TIMER(DN)
/I
TIMER(UP)
I
MON
Current Gain
I
MON
Bandwidth
I
MON
Offset Current
Gate Pull-Up Current
Gate Pull-Down Current
Gate Fast Pull-Down Current
l
l
l
l
l
1.205
10
50
0.55
10
19
2.8
0
4
1.235
20
80
0.62
20
20
3.1
0.4
0
1.235
0.21
–100
2
2
5
250
0
–24
250
140
±1
±10
1.265
30
110
0.7
30
21
3.3
0.8
±10
1.28
0.3
–120
2.6
2.7
5.25
±9
–29
500
V
UV
Falling
l
l
l
V
DD
= 5V,15V, I
LOAD
= 0mA, –10mA
I = 2mA
V = 30V
V
TIMER
Rising
V
TIMER
Falling
V
TIMER
= 0V
V
TIMER
= 1.2V
l
l
l
l
l
l
l
l
l
1.2
0.1
–80
1.4
1.6
4.5
I
OUT
= 600mA
Gate Drive On, V
GATE
= V
OUT
= 12V
Gate Drive Off, V
GATE
= 18V, V
OUT
= 12V
Fast Turn Off, V
GATE
= 18V, V
OUT
= 12V
l
l
l
–18
180
4234fa
For more information
www.linear.com/LTC4234
3
LTC4234
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
DD
= 12V unless otherwise noted.
SYMBOL
PARAMETER
AC Characteristics
Input High (OV), Input Low (UV) to GATE
t
PHL(GATE)
Low Propagation Delay
Short Circuit to GATE Low
t
PHL(ILIM)
t
D(ON)
t
D(FAULT)
t
D(CB)
t
D(COOL_DOWN)
Turn-On Delay
UV Low to Clear Fault Latch Delay
Circuit Breaker Filter Delay Time (Internal)
Cool Down Delay (Internal)
CONDITIONS
V
GATE
< 17.8V Falling
V
FB
= 0, Step V
DD
− SENSE
−
to 50mV, V
GATE
<
15V Falling
Step V
UV
to 2V, V
GATE
> 13V
V
FB
= 0, Step V
DD
− SENSE
−
to 50mV
l
l
l
ELECTRICAL CHARACTERISTICS
MIN
TYP
8
1
MAX
20
5
72
2.7
1200
UNITS
µs
µs
ms
µs
ms
ms
24
1.2
600
l
l
48
1
2
900
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All currents into pins are positive; all voltages are referenced to
GND unless otherwise specified.
Note 3:
An internal clamp limits the GATE pin to a maximum of 6.5V
above OUT. Driving this pin to voltages beyond the clamp may damage the
device.
Note 4:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 5:
T
J
is calculated from the ambient temperature, T
A
, and power
dissipation, P
D
, according to the formula:
T
J
= T
A
+ (P
D
• 15°C/W)
Note 6:
SOA tested at room temperature. SOA (i.e. P
2
t), is reduced at
elevated temperatures according to the following formula:
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