MAX5079EVKIT【PDF 10/18 页】EVAL KIT FOR MAX5079

您好，
买卖IC网欢迎您。
请登录
免费注册

Sheet目录1228

6页 7页 8页 9页 [10页]11页 12页 13页 14页

ORing MOSFET Controller with

Ultra-Fast 200ns Turn-Off

Detailed Description

The MAX5079 ORing MOSFET controller drives an

external n-channel MOSFET and replaces ORing

diodes in high-reliability redundant power-management

systems or multiple paralleled power supplies. The

device has an internal charge pump to drive the high-

side n-channel ORing MOSFET. Additional features

include an adjustable undervoltage lockout threshold

(UVLO), output overvoltage detector (OVI/OVP), input

power-good detector (PGOOD), and two programma-

ble reverse voltage detectors to detect both fast and

slow rises in the reverse voltage across the ORing

MOSFET. The input power-supply range is from 2.75V

to 13.2V or down to 1V when an auxiliary supply of at

least 2.75V is available.

Operational Description

This section describes a detailed startup sequence and

behavior of the MAX5079 under different conditions of

V BUS and V IN . The MAX5079 powers up whenever V IN

is equal to or greater than 2.75V and V UVLO exceeds

the UVLO threshold of 0.66V. Operation with V IN down

to 1V is possible as long as V UVLO ≥ 0.6V and V AUXIN ≥

2.75V.

When V UVLO crosses the UVLO threshold, V GATE rises

to V IN and the charge pump turns on. The charge

pump delivers 2mA to charge the gate capacitance of

the external MOSFET connected to GATE. The constant

gate-charge current prevents large inrush currents from

the input supply. During turn-on, the MAX5079 will

ignore the reverse voltage at IN with respect to BUS.

This is necessary to avoid the unintentional turn-off of

the ORing MOSFET as the momentary inrush current

causes V IN to dip.

Figure 2 shows the MAX5079 in an ORing configuration

with three parallel power supplies (PS1, PS2, and PS3)

and three MAX5079s (U1, U2, and U3) provided by out-

puts V OUT1 , V OUT2 , and V OUT3 . The following events

must be carefully considered to ensure proper function-

ality of the MAX5079 ICs.

1) V BUS is zero with a discharged capacitor (C BUS ).

All three power supplies are turned ON simulta-

neously. V OUT1 comes up before V OUT2 and

V OUT3 .

a. When V OUT1 turns on, the bus capacitors (C BUS )

begin charging from V OUT1 through N1’s body

diode. When V UVLO (U1) rises above the UVLO

threshold, the MAX5079 (U1) charge pump turns

on, and U1 monitors the positive potential from

V OUT1 to V BUS . When V OUT1 ≥ V BUS the charge

pump brings GATE (U1) to 5.5V above V IN (U1) (or

7.5V above V IN depending on the magnitude of

V IN ), by sourcing 2mA into N1’s gate capacitance.

This results in a less than 10μs turn-on time for the

FDB7045L used in the MAX5079 evaluation kit. The

fast turn-on is needed to assure that N1 is ON

before the rising V OUT1 reaches its steady-state

value. If the MOSFET is not turned on before V OUT1

reaches its steady state, V BUS may overshoot due

to the shorting of the 0.7V (forward drop) of N1’s

body diode. A higher V IN (U1) can more quickly

charge the charge-pump capacitor to 5V (or 7V),

while a lower V IN (U1) will take longer. Typically the

MOSFET turns on at V GS = 2.5V. Ensure that the

soft-start time of the power supply is large enough

(> 5ms) to avoid V OUT1 racing ahead and causing

V BUS to overshoot. Care must be taken to avoid the

overloading of V OUT1 by either limiting the source

current (using the current-sharing circuit) or delay

the loading of the BUS until all three power supplies

are up and running.

b. V OUT2 turns on and begins increasing the voltage

at IN (U2). V UVLO (U2) crosses the UVLO thresh-

old, the MAX5079 (U2) charge pump turns on and

U2 monitors the V OUT2 to V BUS voltage. When this

voltage difference becomes positive, GATE (U2)

begins sourcing 2mA into N2’s gate capacitance.

During turn-on, the reverse voltage turn-off circuit

is momentarily disabled. If V OUT2 is lower than

V OUT1 , the external load-sharing controller circuit

of PS2 will try to increase V OUT2 to source current

from V OUT2 . Assume V OUT2 ’s rise time is slow

enough not to cause any overshoot before N2

turns on and starts sharing the current.

c. V OUT3 turns on and U3 follows the same sequence

as U2. Eventually V OUT1 , V OUT2 , and V OUT3 reach

to equilibrium and sharing equal currents.

2) PS1 and PS2 are on and sharing the load when

PS3 is hot-inserted. PS3 will take the same

course as discussed in 1b above.

a. If V OUT3 is higher than V BUS , the BUS voltage will

increase to the new level determined by V OUT3 .

The external load-sharing controller circuit of PS1

and PS2 will increase V OUT1 and V OUT2 to force

current sharing.

b. If V OUT3 is lower than V BUS , the load-sharing cir-

cuit of PS3 will increase V OUT3 to force the sharing

of current. This causes V OUT3 to increases above

V BUS . When this voltage difference becomes posi-

tive, GATE (U3) begins sourcing 2mA into N3’s

gate capacitance. Again, the reverse voltage turn-

off circuit is disabled momentarily, as discussed

before. The load-sharing circuit of PS3’s controller

will adjust V OUT3 so as to share the load current.

10

______________________________________________________________________________________

发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

*型号	*数量	厂商	批号	封装

添加更多采购

我的联系方式

*

*

*

相关PDF资料

MAX5432EVKIT+ KIT EVAL FOR MAX5432

MAX5474EVKIT+ KIT EVAL FOR MAX5474

MAX5488EVKIT# KIT EVALUATION FOR MAX5488

MAX5498EVKIT+ KIT EVAL FOR MAX5498

MAX5946LEVKIT EVAL KIT FOR MAX5946

MAX5960LEVCMAXQU+ KIT EVAL FOR MAX5960

MAX5969AEVKIT# EVAL KIT MAX5969A

MAX5970EVKIT+ EVAL KIT MAX5970

相关代理商/技术参数

MAX507AC/D DIE 制造商:Maxim Integrated Products 功能描述:

MAX507ACNG 功能描述:数模转换器- DAC RoHS:否制造商:Texas Instruments 转换器数量:1 DAC 输出端数量:1 转换速率:2 MSPs 分辨率:16 bit 接口类型:QSPI, SPI, Serial (3-Wire, Microwire) 稳定时间:1 us 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-14 封装:Tube

MAX507ACNG+ 功能描述:数模转换器- DAC 12-Bit Precision DAC RoHS:否制造商:Texas Instruments 转换器数量:1 DAC 输出端数量:1 转换速率:2 MSPs 分辨率:16 bit 接口类型:QSPI, SPI, Serial (3-Wire, Microwire) 稳定时间:1 us 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-14 封装:Tube

MAX507ACWG 功能描述:数模转换器- DAC RoHS:否制造商:Texas Instruments 转换器数量:1 DAC 输出端数量:1 转换速率:2 MSPs 分辨率:16 bit 接口类型:QSPI, SPI, Serial (3-Wire, Microwire) 稳定时间:1 us 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-14 封装:Tube

MAX507ACWG+ 功能描述:数模转换器- DAC 12-Bit Precision DAC RoHS:否制造商:Texas Instruments 转换器数量:1 DAC 输出端数量:1 转换速率:2 MSPs 分辨率:16 bit 接口类型:QSPI, SPI, Serial (3-Wire, Microwire) 稳定时间:1 us 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-14 封装:Tube

MAX507ACWG+T 功能描述:数模转换器- DAC 12-Bit Precision DAC RoHS:否制造商:Texas Instruments 转换器数量:1 DAC 输出端数量:1 转换速率:2 MSPs 分辨率:16 bit 接口类型:QSPI, SPI, Serial (3-Wire, Microwire) 稳定时间:1 us 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-14 封装:Tube

MAX507ACWG-T 功能描述:数模转换器- DAC RoHS:否制造商:Texas Instruments 转换器数量:1 DAC 输出端数量:1 转换速率:2 MSPs 分辨率:16 bit 接口类型:QSPI, SPI, Serial (3-Wire, Microwire) 稳定时间:1 us 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-14 封装:Tube

MAX507AENG 功能描述:数模转换器- DAC RoHS:否制造商:Texas Instruments 转换器数量:1 DAC 输出端数量:1 转换速率:2 MSPs 分辨率:16 bit 接口类型:QSPI, SPI, Serial (3-Wire, Microwire) 稳定时间:1 us 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-14 封装:Tube