DPA422R View Datasheet(PDF) - Power Integrations, Inc

Part Name

Description

MFG CO.

DPA422R

Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications

Power Integrations, Inc 

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DPA422-426

Ethernet

(RJ-45) D101

Connector DL4002

(1,2)

DL4002

D102

D103

DL4002

(4,5)

DL4002

D104

D105

DL4002

(3,6)

DL4002

D106

D107

DL4002

(7,8)

DL4002

D108

PoE Interface

VR51

28 V

R52

20 kΩ

R51

24.9 kΩ

1% 1/4 W

D51

BAV19

C51

1 nF

50 V

D52

BAV19

R53

20 kΩ

R54

20 Ω

Q51

TIP29C (100 V/1 A)

or MMBTA06

L1

1 µH 2.5 A

R1

649 kΩ

1%

C1

1 µF

100 V

C2

1 µF

100 V

VR1

SMAJ

150

D41

BAV19WS

1

3

4

T1

4

3

D31

20CJQ060

8

7

6

Q22

7

Si4804

6 C21

2.2 nF

R21

10 Ω

R22

10 Ω

5

R23

174 k

1%

Q21 VR21

Si4804

R23

10 kΩ

L2

16 µH 4 A

8

5

7

2

D6

BAV

19WS

D21

SL13

15 V

C6

4.7 µF

20 V

R21

10 k

Q20

MMBTS3906

R22

10 kΩ

U2

PC357

N1T

DPA-Switch

U1

D

L DPA424PN

CONTROL

C

S

XF

C4

220 nF

R2

13.3 kΩ

1%

R3

1.0 Ω

C5

47 µF

10 V

C41

4.7 µF, 35 V

VR41 D42

6.8 V IN4148

20 V, 10 mA

C31

100 µF

10 V

C22-C24

100 µF 5 V

7.5 V, 0.4 A

C25

R4 1 µF

160 Ω 10 V 5 V, 2.4 A

RTN

R11

10 kΩ

U2

R16

10 kΩ

1%

R12

150 Ω

D11

BAV19WS

C11

2.2 µF

10 V

U3

LM431AIM3

C12

100 nF

R13

11 Ω

C13 R14

68 nF 1 kΩ

R15

10 kΩ

1%

PI-3824-031008

Figure 27. PoE Interface Circuit Using a Bipolar Transistor Pass-Switch and DPA424P.

controlled pass-switch. By adding this circuitry to the front end

of a DPA converter, a low cost and low component count PoE

powered device (PD) power supply can be implemented.

Figure 27 shows a typical PD solution.

The PoE specification requires the PD to provide three

fundamental functions: discovery, classification, and pass-

switch connection.

When input voltage is applied to the PD, it must present the

correct discovery signature impedance in the voltage range of

2.5 VDC to 10 VDC. This impedance is provided by R51 in

Figure 27.

The second “classification” phase occurs at input voltages

15 VDC to 20 VDC. The PD must draw a specified current to

identify the device class (Class 0 specifies 0.5 mA to 4 mA).

This is again accomplished by resistor R51.

In the third phase, the bipolar pass-switch (Q51 in Figure 27)

connects the input voltage to the power supply at voltages

above approximately 30 VDC (28 V+VR52). Zener diode VR51

conducts, driving the current through resistor R52 to the base

of Q51. Resistor R53 prevents turn-on under other conditions.

Once the Power supply has started, components D51, D52,

C51 and R54 enhance the base-current drive by coupling

power from the power supply bias winding.

Once the three start up phases have been successfully

completed, the DPA-Switch is allowed to function as a forward

converter (described in Figure 25 and accompanying text).

Key Application Considerations

DPA-Switch Design Considerations

Power Table

This section provides a description of the assumptions used to

generate the power tables (Tables 1 and 3 through 6) and

explains how to use the information provided by them.

All Power tables: Tables 1 and 3 through 6

• Maximum output power is limited by the device internal

current limit. This is the peak output power which could

become the continuous output power, provided adequate

heat sinking is used.

• Data assumes adequate heat sinking to keep the junction

temperature at or below 100 °C and worst case RDS(ON) at

TJ = 100 °C.

• The use of P and G packages are recommended for device

dissipation equal to or less than 1.5 W only due to package

thermal limitation. For device dissipation above 1.5 W, use

R package.

16

Rev. T 12/12

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