LT3579IUFD-1-PBF データシートの表示（PDF） - Linear Technology

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LT3579IUFD-1-PBF

6A Boost/Inverting DC/DC Converter with Fault Protection

Linear Technology 

LT3579/LT3579-1

APPLICATIONS INFORMATION

HOT PLUG

L1

D1

C1

D3

VIN

The high inrush current associated with hot-plugging VIN

can be largely rejected with the use of an external PMOS. A

SW1 SW2

–VOUT

D2

RFB

simple hot-plug controller can be designed by connecting

an external PMOS in series with VIN, with the gate of the

100k

VIN

FB

SHDN

GATE

LT3579

COUT

PMOS being driven by the GATE pin of the LT3579. Since

FAULT

CLKOUT

the GATE pin pull-down current is linearly proportional to

CIN

RT

VC

the SS voltage, and the SS charge up time is relatively slow,

the GATE pin pull-down current will increase gradually,

SYNC GND SS

RT

CSS

RC

CF

CC

thereby turning on the external PMOS slowly. Controlled

3579 F15

in this manner, the PMOS acts as an input current limiter

when VIN hot-plugs or ramps up sharply.

Figure 15. Single Inductor Inverting Topology

Likewise, when the PMOS is connected in series with the

output, inrush currents into the output capacitor can be

limited during a hot-plug event. To illustrate this, the circuit

in Figure 6 was re-configured by adding a large 1500μF

capacitor to the output. An 18Ω resistive load was used

4.7μF

4.7μF

4.7μF

VOUT2

100V

200mA

VOUT1

67V

100mA

and a 2.2μF capacitor was placed on SS. Figure 14 shows

4.7μF

the result of hot-plugging this re-configured circuit. The

inductor current is well behaved and VOUT comes up once VIN

10μH

VIN settles out.

12V

6.8μF

VIN

5V/DIV

VOUT

10V/DIV

IL

5A/DIV

SS

1V/DIV

SW1 SW2

383k 6.5k

100k

VIN

FAULT

FB

GATE

VIN

LT3579

536k SHDN

CLKOUT

10μF

RT

VC

SYNC GND SS

27pF

34k

86.6k

2.2μF

470pF

6.8μF

1s/DIV

3579 F14

Figure 14. VIN Hot-Plug Control. Inrush Current is Well Controlled

3579 F16

Figure 16. High VOUT Charge Pump Topology

35791f

23

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