KIT34712EPEVBE【PDF 15/24 页】KIT EVAL BOARD 3A 1MHZ

您好，
买卖IC网欢迎您。
请登录
免费注册

11页 12页 13页 14页 [15页]16页 17页 18页 19页

FUNCTIONAL DEVICE OPERATION

PROTECTION AND DIAGNOSTIC FEATURES

and the buck converter switching frequency value is

determined by reading the FREQ pin. A soft start cycle is then

initiated to ramp up the output of the buck converter (V TT ).

The buck converter error amplifier uses the voltage on the

VREFOUT pin (V REF ) as its reference voltage. V REF is equal

to 1/2 V DDQ , where V DDQ is applied to the VREFIN pin. This

way, the 34712 assures that V REF and V TT voltages track 1/2

V DDQ to meet DDR requirements.

Soft start is used to prevent the output voltage from

overshooting during startup. At initial startup, the output

capacitor is at zero volts; V OUT = 0 V. Therefore, the voltage

across the inductor will be PV IN during the capacitor charge

phase which will create a very sharp di/dt ramp. Allowing the

inductor current to rise too high can result in a large

difference between the charging current and the actual load

current that can result in an undesired voltage spike once the

the IC goes out of standby or shutdown mode, power is

recycled, or after a fault retry.

To fully take advantage of soft starting, it is recommended

not to enable the 34712 output before introducing VDDQ on

the VREFIN pin. If this happens after a soft start cycle expires

and the VREFIN voltage has a high dv/dt, the output will

naturally track it immediately and ramp up with a fast dv/dt

itself and that will defeat the purpose of soft starting. For

reliable operation, it is best to have the VDDQ voltage

available before enabling the output of the 34712.

After a successful start-up cycle where the device is

enabled, no faults have occurred, and the output voltage has

reached its regulation point, the 34712 pulls the power good

output signal low after a 10ms reset delay, to indicate to the

host that the device is in normal operation.

capacitor is fully charged. The soft start is active each time

PROTECTION AND DIAGNOSTIC FEATURES

The 34712 monitors the application for several fault

conditions to protect the load from overstress. The reaction of

the IC to these faults ranges from turning off the outputs to

just alerting the host that something is wrong. In the following

paragraphs, each fault condition is explained:

Output Over-voltage

An over-voltage condition occurs once the output voltage

goes higher than the rising over-voltage threshold (V OVR ). In

this case, the power good output signal is pulled high, alerting

the host that a fault is present, but the V TT and V REF outputs

will stay active. To avoid erroneous over-voltage conditions,

a 20 μs filter is implemented. The buck converter will use its

feedback loop to attempt to correct the fault. Once the output

voltage falls below the falling over-voltage threshold (V OVF ),

the fault is cleared and the power good output signal is pulled

low, the device is back in normal operation.

Output Under-voltage

An under-voltage condition occurs once the output voltage

falls below the falling under-voltage threshold (V UVF ). In this

case, the power good output signal is pulled high, alerting the

host that a fault is present, but the V TT and V REF outputs will

stay active. To avoid erroneous under-voltage conditions, a

20 μs filter is implemented. The buck converter will use its

feedback loop to attempt to correct the fault. Once the output

voltage rises above the rising under-voltage threshold

(V UVR ), the fault is cleared and the power good output signal

is pulled low, the device is back in normal operation.

Output Over-current

This block detects over-current in the Power MOSFETs of

the buck converter. It is comprised of a sense MOSFET and

a comparator. The sense MOSFET acts as a current

detecting device by sampling a ratio of the load current. That

sample is compared via the comparator with an internal

reference to determine if the output is in over-current or not.

current limit (I LIM ), the converter will start a cycle-by-cycle

operation to limit the current, and a 10 ms over-current limit

timer (t LIM ) starts. The converter will stay in this mode of

operation until one of the following occurs:

? The current is reduced back to the normal level before

t LIM expires, and in this case normal operation is

regained.

? t LIM expires without regaining normal operation, at

which point the device turns off the output and the

power good output signal is pulled high. At the end of a

timeout period of 100 ms (t TIMEOUT ), the device will

attempt another soft start cycle.

? The device reaches the thermal shutdown limit (T SDFET )

and turns off the output. The power good output signal

is pulled high.

Short-circuit Current Limit

This block uses the same current detection mechanism as

the over-current limit detection block. If the load current

reaches the I SHORT value, the device reacts by shutting down

the output immediately. This is necessary to prevent damage

in case of a permanent short circuit. Then, at the end of a

timeout period of 100 ms (t TIMEOUT ), the device will attempt

another soft start cycle.

Thermal Shutdown

Thermal limit detection block monitors the temperature of

the device and protects against excessive heating. If the

temperature reaches the thermal shutdown threshold

(T SDFET ), the converter output switches off and the power

good output signal indicates a fault by pulling high. The

device will stay in this state until the temperature has

decreased by the hysteresis value and then After a timeout

period (T TIMEOUT ) of 100 ms, the device will retry

automatically and the output will go through a soft start cycle.

If successful normal operation is regained, the power good

output signal is asserted low to indicate that.

If the peak current in the output inductor reaches the over

34712

Analog Integrated Circuit Device Data ?

Freescale Semiconductor

15

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

KIT34713EPEVBE KIT EVAL BOARD 5A 1MHZ

KIT34716EPEVBE KIT EVAL BOARD 1MHZ DUAL SW-MODE

KIT34717EPEVBE KIT EVAL BOARD 5A 1.0MHZ

KS-1787-MG SHELF SLIDING KEYBOARD ASSEMBLY

KS-1788 SHELF SLIDING KEYBOARD ASSEMBLY

KSDKSTM32-PL KIT IAR KICKSTART STM32 CORTEXM3

LC4064ZC-EV BOARD EVAL FOR ISPMACH 4064ZC

LCMXO2280C-C-EVN BOARD CONTROL EVAL MACHXO

相关代理商/技术参数

KIT34713EPEVBE 功能描述:电源管理IC开发工具 5.0 A 1.0 MHZ FULLY INTEG RoHS:否制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V

KIT34716EPEVBE 功能描述:电源管理IC开发工具 1.0 MHZ DUAL SWITCH-MODE RoHS:否制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V

KIT34717EPEVBE 功能描述:电源管理IC开发工具 5.0 A 1.0MHZ FULLY INTEG RoHS:否制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V

KIT34727FCEVBE 功能描述:电源管理IC开发工具 600MA HIGH EFFICIENCY LO RoHS:否制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V

KIT34825EPEVME 功能描述:界面开发工具 MICRO USB INTERFACE IC RoHS:否制造商:Bourns 产品:Evaluation Boards 类型:RS-485 工具用于评估:ADM3485E 接口类型:RS-485 工作电源电压:3.3 V

KIT34844AEPEVBE 功能描述:LED 照明开发工具 IC, 10 CHANNEL LED BACKLIGHT RoHS:否制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装:

KIT34844EPEVME 功能描述:LED 照明开发工具 MC34844 10-Ch LED BL Driver Eval Kit RoHS:否制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装:

KIT34845EPEVME 功能描述:LED 照明开发工具 IC, 6 CHANNEL LED BACKL RoHS:否制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: