MCP18480 Datasheet, PDF(39/64 Page) Microchip Technology

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MCP18480 Datasheet, PDF (39/64 Pages) Microchip Technology – -48V Hot Swap Controller

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4.0 APPLICATIONS INFORMATION

The MCP18480 can be programmed to have the PWR-

GOOD signal be either active-high or active-low via the

ISET pin and the connection of the external RISET resis-

tor (see Section 6.8.8, âBias Blockâ). If the RISET resis-

tor is connected between ISET and VNEG, the

PWRGOOD output pin is an active-high signal. If the

RISET resistor is connected between ISET and VREFIN,

the PWRGOOD output pin is an active-low signal.

For systems using an active-low-enabled DC/DC con-

verter module, the MCP18480 should be programmed

for a high-active PWRGOOD output. Tying the RISET

resistor to the VNEG pin configures the PWRGOOD to

be an active-high signal. The active-high PWRGOOD

switches on the external NPN and the collector of the

external NPN (labeled as GOODPWR) is pulled to

VNEG, enabling a low-active GOODPWR and resulting

in enabling the DC/DC module.

MCP18480

For active-high DC/DC converter modules, the

MCP18480 should be programmed for a low active

PWRGOOD output. Connecting RISET to the VREFIN

pin will enable an active-low PWRGOOD output. Refer

to Figure 4-1 and Figure 4-2 for schematics.

Figure 4-1 shows a typical telecom application circuit

where the DC/DC module is active-high. Figure 4-2

shows a typical telecom application circuit where the

DC/DC module is active-low. The polarity of the

MCP18480âs PWRGOOD pin (active-high or active-

low) is dependant on the state of the ISET pin.

GND

RPOS

ROV1

4 kâ¦ 1.74 Mâ¦

CBYP1 +

2 ÂµF

CBYP2

10 nF

78V

Transorb

ROV2

59 kâ¦

Fuse 10A

VNEG

RUV1

453 kâ¦

RUV2

30.9 kâ¦

RUVHYS

280 kâ¦

CUVD

800 nF

RISET

124 kâ¦

24.9 kâ¦

1 VPOS

2 OVTH

3 UVTH

4 UVHYS

5 UVD

6 VREFOUT

7 VREFIN

8 CL

9 ISET

10 TIMER

RESTART 20

ENABLE 19

PWRGOOD 18

OVO 17

DRAINTH 16

VFB 15

GATE 14

SENSE 13

RDISCH 12

VNEG 11

Ctimer

680 nF

MCP18480

SRS

SEN

RPG1

110 kâ¦

5V RPG3

680â¦

RPG4

36 kâ¦ QPG1

MPSA43

RBYPL

51 kâ¦

VIN+

CBYPL

100 ÂµF

100 V

VOUT+

DC/DC

Converter

QPG2

Module

2N5400 GOODPWR

RPG5

36 kâ¦

QPG3

ON/OFF

VIN- VOUT-

RPG6

NTE261

1500â¦

RDISCH

1.6 Mâ¦

RPG2

7.5 kâ¦

RSENSE

0.01â¦

CG1

RG1

100 nF 10â¦

RGD

18 kâ¦

CGD

3.3 nF

NTE2388

RFB2

124 kâ¦

RFB1

1.74 Mâ¦

RDRAIN2

115 kâ¦

RDRAIN1

1.6 Mâ¦

FIGURE 4-1:

Typical Operating Circuit for Telecom Applications with Active-High power Module -

foldback current limit enabled.

DS20091B-page 39

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