Datasheet > DPA425P-TL

DPA425P-TL

更新时间： 2024-09-16 22:29:47

品牌	Logo	应用领域
帕沃英蒂格盛 - POWERINT		转换器
页数	文件大小	规格书
36页	289K
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Highly Integrated DC-DC Converter ICs for Distributed Power Architectures

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DPA425P-TL 数据手册

DPA423-426

approximately 5.8 V, the control circuitry is activated and the

soft-start begins. The soft-start circuit gradually increases the

duty cycle of the MOSFET from zero to the maximum value

over approximately 5 ms. The high voltage current source is

turned off at the end of the soft-start. If no external feedback/

supply current is fed into the CONTROL pin by the end of the

soft-start, the CONTROL pin will start discharging in response

to the supply current drawn by the control circuitry and the gate

current of the switching MOSFET driver. If the power supply

is designed properly, and no fault condition such as open loop

or overloaded output exists, the feedback loop will close,

providing external CONTROL pin current, before the

CONTROL pin voltage has had a chance to discharge to the

lowerthresholdvoltageofapproximately4.8V(internalsupply

under-voltage lockout threshold). When the externally fed

current charges the CONTROL pin to the shunt regulator

voltage of 5.8 V, current in excess of the consumption of the

chip is shunted to SOURCE through resistor R_Eas shown in

Figure 2. This current flowing through R_Econtrols the duty

cycle of the power MOSFET to provide closed loop regulation.

The shunt regulator has a finite low output impedance Z_Cthat

sets the gain of the error amplifier when used in a primary

feedback configuration. The dynamic impedance Z_Cof the

CONTROL pin together with the external CONTROL pin

capacitance sets the dominant pole for the control loop.

currentstandbymode. Thehigh-voltagecurrentsourceturnson

and charges the external capacitance again. A hysteretic

internal supply under-voltage comparator keeps V_Cwithin a

window of typically 4.8 to 5.8 V by turning the high-voltage

current source on and off as shown in Figure 5. The auto-restart

circuit has a divide-by-8 counter that prevents the output

MOSFET from turning on again until eight discharge/charge

cycles have elapsed. This is accomplished by enabling the

output MOSFET only when the divide-by-8 counter reaches

full count (S7). The counter effectively limits DPA-Switch

power dissipation as well as the maximum power delivered to

the power supply output by reducing the auto-restart duty cycle

to typically 4%. Auto-restart mode continues until output

voltage regulation is again achieved through closure of the

feedback loop.

Oscillator and Switching Frequency

Theinternaloscillatorlinearlychargesanddischargesaninternal

capacitance between two voltage levels to create a sawtooth

waveform for the pulse width modulator. The oscillator sets

both the pulse width modulator latch and the current limit latch

at the beginning of each cycle.

The nominal switching frequency of 400 kHz was chosen to

minimize the transformer size and to allow faster power supply

loop response. The FREQUENCY pin, when shorted to the

CONTROL pin, lowers the switching frequency to 300 kHz,

which may be preferable in some applications such as those

employing secondary synchronous rectification. Otherwise,

theFREQUENCYpinshouldbeconnectedtotheSOURCEpin

for the default 400 kHz.

When a fault condition such as an open loop or overloaded

output prevents the flow of an external current into the

CONTROLpin,thecapacitorontheCONTROLpindischarges

towards4.8V. At4.8Vauto-restartisactivatedwhichturnsthe

output MOSFET off and puts the control circuitry in a low

V_UV

V_LINE

0 V

S7 S0

S1 S2

5.8 V

4.8 V

V_C

0 V

V_DRAIN

0 V

V_OUT

0 V

Note: S0 through S7 are the output states of the auto-restart counter

PI-2545-050602

Figure 5. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down.

1/04

1 2 3 456 7 8...36

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与DPA425P-TL相关器件

型号	品牌	获取价格	描述	数据表
DPA425R	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications
DPA425R-TL	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Distributed Power Architectures
DPA426	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Distributed Power Architectures
DPA426G	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications
DPA426GN	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications
DPA426GN-TL	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications
DPA426G-TL	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications
DPA426P	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications
DPA426PN	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications
DPA426R	POWERINT	获取价格	Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications

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