参数资料
型号: LTC4252A-2CMS#TRPBF
厂商: LINEAR TECHNOLOGY CORP
元件分类: 电源管理
英文描述: Negative Voltage Hot Swap Controllers; Package: MSOP; No of Pins: 10; Temperature Range: 0°C to +70°C
中文描述: 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO10
封装: LEAD FREE, PLASTIC, MSOP-10
文件页数: 9/36页
文件大小: 394K
代理商: LTC4252A-2CMS#TRPBF
LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
17
425212fb
of 2.5% or more will eventually trip the circuit breaker and
shut down the LTC4252. Figure 5 shows the circuit breaker
response time in seconds normalized to 1
F for IDRN =
0
A. The asymmetric charging and discharging of CT is a
fair gauge of MOSFET heating.
The normalized circuit response time is estimated by
t
CF
ID
T
DRN
()
.
.
=
+
()
[]
4
235 8 8
5 8
(4)
SHUTDOWN COOLING CYCLE
For the LTC4252-1 (latchoff version), TIMER latches high
with a 5.8
A pull-up after the circuit breaker fault TIMER
reaches 4V. For the LTC4252-2 (automatic retry version),
a shutdown cooling cycle begins if TIMER reaches the 4V
threshold. TIMER starts with a 5.8
A pull-down until it
reaches the 1V threshold. Then, the 5.8
A pull-up turns
back on until TIMER reaches the 4V threshold. Four 5.8
A
pull-down cycles and three 5.8
A pull-up cycles occur
between the 1V and 4V thresholds, creating a time interval
given by:
t
VC
A
SHUTDOWN
T
=
73
58
.
(5)
At the 1V threshold of the last pull-down cycle, a GATE
ramp-up is attempted.
SOFT-START
Soft-start limits the inrush current profile during GATE
start-up. Unduly long soft-start intervals can exceed the
MOSFET’s SOA rating if powering up into an active load. If
SS floats, an internal current source ramps SS from 0V to
2.2V for the LTC4252 or 0V to 1.4V for the LTC4252A in
about 230
s. Connecting an external capacitor CSS from
SS to ground modifies the ramp to approximate an RC
response of:
Vt
V
e
SS
t
RC
SS
()
1
(6)
An internal resistive divider (95k/5k for the LTC4252 or
47.5k/2.5k for the LTC4252A) scales VSS(t) down by 20
times to give the analog current limit threshold:
Vt
V
ACL
SS
OS
()
=
20
(7)
This allows the inrush current to be limited to VACL(t)/RS.
The offset voltage, VOS (10mV), ensures CSS is sufficiently
discharged and the ACL amplifier is in current limit before
GATE start-up. SS is pulled low under any of the following
conditions: in UVLO, in an undervoltage condition, in an
overvoltage condition, during the initial timing cycle or
when the circuit breaker fault times out.
GATE
GATE is pulled low to VEE under any of the following
conditions: in UVLO, in an undervoltage condition, in an
overvoltage condition, during the initial timing cycle or
when the circuit breaker fault times out. When GATE turns
on, a 58
A current source charges the MOSFET gate and
any associated external capacitance. VIN limits the gate
drive to no more than 14.5V.
Gate-drain capacitance (CGD) feedthrough at the first
abrupt application of power can cause a gate-source
voltage sufficient to turn on the MOSFET. A unique circuit
pulls GATE low with practically no usable voltage at VIN
APPLICATIO S I FOR ATIO
WU
U
Figure 5. Circuit-Breaker Response Time
FAULT DUTY CYCLE (%)
0
20406080
100
NORMALIZED
RESPONSE
TIME
(s/
F)
10
1
0.1
0.01
4252-1/2 F05
=
4
[(235.8 + 8 IDRN) D – 5.8]
t
CT(F)
IDRN = 0A
相关PDF资料
PDF描述
LTC4252A-2IMS#PBF Negative Voltage Hot Swap Controllers; Package: MSOP; No of Pins: 10; Temperature Range: -40°C to +85°C
LTC4252A-2IMS#TRPBF Negative Voltage Hot Swap Controllers; Package: MSOP; No of Pins: 10; Temperature Range: -40°C to +85°C
LTC4252-2CMS8#PBF Negative Voltage Hot Swap Controllers; Package: MSOP; No of Pins: 8; Temperature Range: 0°C to +70°C
LTC4252-2CMS8#TRPBF Negative Voltage Hot Swap Controllers; Package: MSOP; No of Pins: 8; Temperature Range: 0°C to +70°C
LTC4252-2IMS8#PBF Negative Voltage Hot Swap Controllers; Package: MSOP; No of Pins: 8; Temperature Range: -40°C to +85°C
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LTC4252A-2IMSPBF 制造商:LINER 制造商全称:Linear Technology 功能描述:Negative Voltage Hot Swap Controllers