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参数资料
| 型号： | LTC4245CG#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/36页 |
| 文件大小： | 431K |
| 描述： | IC CNTRLR HOT SWAP 36-SSOP |
| 标准包装： | 1,000 |
| 类型： | 热交换控制器 |
| 应用： | CompactPCI? |
| 内部开关： | 无 |
| 电源电压： | 3.3V，5V，12V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 36-SSOP |
| 包装： | 带卷 (TR) |
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LTC4245
13
4245fa
OPERATIO
Start-Up
The LTC4245 is designed to turn a boards supply voltages
on and off in a controlled manner, allowing the board to be
safely inserted or removed from a live backplane slot. When
a supply turn-on command is received, current sources
start pulling up the TIMER and SS pins. The 100糀 I
TMR
current and the external TIMER capacitor determine the
time a supply can be in current limit during start-up. The
gate of a supplys external N-channel MOSFET is servoed
by an amplifer (ACL
n
) so that the current, as indicated by
the sense resistor voltage drop, never exceeds an internal
current limit. This current limit rises at a rate determined
by I
SS
and the capacitor at the SS pin. A foldback circuit
determines the maximum value of the current limit and
reduces it to 30% of the maximum when a supplys output
is shorted to ground. When the TIMER pin crosses 2.56V
it is reset to ground and the start-up timing cycle ends. If
a supply is still in current limit all gates are turned off, an
overcurrent fault is logged and the TIMER goes through
a cool-down timing cycle using 2糀 for I
TMR
. Otherwise,
its circuit breaker (ECB
n
) is armed and the current limit
is raised to 3 times the circuit breaker threshold. The SS
pin is then reset by switch M2.
Any combination of the four supplies can be turned on
together or one after another. Whenever a supply is ramp-
ing up, its output voltage will affect, through the foldback
circuit, where the internal current limit ramp stops. The
default con guration turns on all supplies together. If
sequence control bit C6 (Table 9) is set, the supplies turn
on in a 12V, 5V, 3.3V, 12V sequence. With this bit set,
the end of a supply ramp-up triggers the start of the next
one in the sequence. The I
2
C interface allows independent
on and off control for each supply through its On control
bit. Turn-off is simultaneous under fault conditions and
when using the ON or BD_SEL# pins.
At the end of the last start-up timing cycle, HEALTHY#
is pulled low by M3 if all supply outputs are above their
power bad thresholds. LOCAL_PCI_RST# which was held
low (M4), now follows PCI_RST#. The TIMER pin goes
through a PGI timeout cycle using 10糀 for I
TMR
. The PGI
pin is sampled at the end of the cycle. If it is low, then
all external MOSFETs are shut-off, a PGI fault is logged
and TIMER goes through a cool-down cycle using 2糀
for I
TMR
. If PGI is high, the part enters the normal mode
of operation.
Normal Operation
During normal operation, the gates of the MOSFETs are
clamped about 6.2V above their sources. The 12V gate
driver uses a charge pump, the 5V and 3.3V gate drive is
derived from 12V
IN
and the 12V gate drive from INTV
CC
.
Each supply is continuously monitored for undervoltage,
overcurrent and power bad conditions. Overcurrent moni-
toring consists of an electronic circuit breaker comparator
(ECB
n
) and an active current limit circuit (ACL
n
) set at 3x the
ECB threshold. Undervoltage and overcurrent faults cause
all MOSFETs to be shut off. A power bad condition causes
HEALTHY# to go high impedance and LOCAL_PCI_RST#
to pull low, without shutting off the MOSFETs. If the PGI
pin is not disabled (register bit C3 not set), then PGI pin
going low will also shut off all MOSFETs.
ADC
Included in the LTC4245 is an 8-bit A/D converter. The
converter has a 13-input multiplexer to select between
input, output and current sense voltage of each supply,
and the GPIO channel. The ADC can either cycle through
all channels or measure a channel on-demand.
Serial Interface
An I
2
C interface is provided to read from or write to the
status, control and A/D registers. It allows the host to poll
the device and determine if faults have occurred. If the
ALERT# line is used as an interrupt, the host can respond
to a fault in real time. The LTC4245 I
2
C interface slave ad-
dress is decoded using the ADR0 to ADR3 pins.
Con guration, GPIO and Precharge
The three-state CFG pin can be used to disable the V
EE
undervoltage lockout, power bad and foldback functions.
It can also convert the 5V undervoltage, power bad and
ADC levels to 3.3V levels. The GPIO1 to GPIO3 pins can
be used as general purpose inputs or outputs (M5 to
M7). One of the pins can also be multiplexed to the GPIO
channel of the ADC. A 1V reference voltage derived from
3V
IN
is provided at the PRECHARGE pin. This can be used
to pre-charge I/O lines on the board so as not to corrupt
the backplane bus.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4245CUHF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Multiple Supply Hot Swap Controller with I2C Compatible Monitoring |
| LTC4245CUHF#PBF | 功能描述:IC CNTRLR HOT SWAP 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4245CUHF#TRPBF | 功能描述:IC CNTRLR HOT SWAP 38-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4245IG | 制造商:LINER 制造商全称:Linear Technology 功能描述:Multiple Supply Hot Swap Controller with I2C Compatible Monitoring |
| LTC4245IG#PBF | 功能描述:IC CNTRLR HOT SWAP 36-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
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