LT4256-1 LINER [Linear Technology], LT4256-1 Datasheet - Page 14

• Manufacturer Part Number: LT4256-1
• Description: Positive High Voltage Hot Swap Controllers
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
LT4256-1/LT4256-2
Notes on Using the LT4256 in LT1641 Applications
Even though the LT4256 and LT1641 have the same
pinout, several changes were made to improve overall
system accuracy and increase noise immunity. These
changes are spelled out in Table 1 and must be accounted
for if using the LT4256 in an LT1641 application.
Layout Considerations
To achieve accurate current sensing, a Kelvin connection
to the current sense resistor (R5 in typical application
Table 1. Differences Between LT1641 and LT4256
SPECIFICATION
UV Threshold
FB Threshold
TIMER Current
TIMER Shutdown V
GATE I
GATE Resistor
Foldback I
I
14
LIM
Threshold
PU
LIM
GND
V
U
IN
(SHORT PIN)
LT1641
1.233V
1.233V
1.233V
12mV
47mV
10 A
U
1k
70%
0.1 F
C3
Figure 14. Negative Output Voltage Protection Diode Application
SMAT70A
W
LT4256
3.99V
4.65V
14mV
55mV
100
30 A
26%
R1
64.9k
R2
8.06k
4V
D2
C2
33nF
1
5
U
UV
TIMER
Slightly Different Current Limit Trip Point
COMMENTS
Higher 1% Reference for Better Noise Immunity and System Accuracy
Higher 1% Reference for Better Noise Immunity and System Accuracy
More Accurate TIMEOUT
Higher Trip Voltage for Better Noise Immunity
Higher Current to Accommodate Higher Leakage MOSFETs or Parallel Devices
Different Compensation for Current Limit Loop
Slightly Different Current Limit Trip Point
V
LT4256-1/
CC
LT4256-2
8
0.033
GND
R5
4
SENSE
PWRGD
GATE
7
FB
6
2
3
circuit) is recommended. The minimum trace width for
1oz copper foil is 0.02" per amp to make sure the trace
stays at a reasonable temperature. 0.03" per amp or wider
is recommended. Note that 1oz copper exhibits a sheet
resistance of about 530
cause large errors in high current applications. Noise
immunity will be improved significantly by locating resis-
tor dividers close to the pins with short V
traces. A 0.1 F decoupling capacitor from UV to GND is
also required.
IRF530
UV = 36V
PWRGD = 40V
Q1
R7
100
R6
10
C1
10nF
D1
CMPZ5241B
11V
R8
36.5k
R9
4.02k
4256 F14
R4
27k
/ . Small resistances can
C
100 F
D3
MRA4003T3
L
V
OUT
CC
and GND
425612f