1640AL Просмотр технического описания (PDF) - Linear Technology

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1640AL

Negative Voltage Hot Swap Controller

Linear Technology 

LT1640AL/LT1640AH

APPLICATIO S I FOR ATIO

Undervoltage and Overvoltage Detection

The UV (Pin 3) and OV (Pin 2) pins can be used to detect

undervoltage and overvoltage conditions at the power

supply input. The UV and OV pins are internally connected

to analog comparators with 20mV of hysteresis. When the

UV pin falls below its threshold or the OV pin rises above

its threshold, the GATE pin is immediately pulled low. The

GATE pin will be held low until UV is high and OV is low.

The undervoltage and overvoltage trip voltages can be

programmed using a three resistor divider as shown in

Figure 10a. With R4 = 562k, R5 = 9.09k and R6 = 10k, the

undervoltage threshold is set to 37V and the overvoltage

threshold is set to 71V. The resistor divider will also

amplify the 20mV hysteresis at the UV pin and OV pin to

0.6V and 1.2V at the input, respectively.

More hysteresis can be added to the UV threshold by

connecting resistor R3 between the UV pin and the GATE

pin as shown in Figure 10b.

(SHORT PIN)

GND

GND

R4

( ) VUV

=

1.223

R4 + R5+ R6

R5 + R6

R5

( ) VOV

=

1.223

R4

+ R5+

R6

R6

R6

– 48V

8

VDD

3

UV

LT1640AL

2

LT1640AH

OV

VEE

4

1640A F10a

Figure 10a. Undervoltage and Overvoltage Sensing

(SHORT PIN)

GND

GND

R4

506k

1%

UV = 37.6V

R1

UV = 43V

562k

OV = 71V

1%

R5 R2

8.87k 16.9k

1% 1%

*

– 48V

* DIODES INC. SMAT70A

R3

1.62M

1%

8

VDD

2

OV

3

UV

LT1640AL /LT1640AH

VEE

SENSE

GATE

4

5

6

R1

3

0.02Ω

5%

4

C1

R6

150nF 10Ω

25V

5%

1

2

Q1 1640A F10b

IRF530

Figure 10b. Programmable Hysteresis for Undervoltage Detection

11

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