LTC2921CGN データシートの表示（PDF） - Linear Technology

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LTC2921CGN

Power Supply Tracker with Input Monitors

Linear Technology 

LTC2921/LTC2922 Series

APPLICATIO S I FOR ATIO

VOUT

VFB

5V = 7.5%

DC/DC

CONVERTER

RX0

100Ω

VOUT 3.3V = 7.5%

VFB

DC/DC

CONVERTER

RX1

100Ω

VOUT 2.5V = 7.5%

VFB

DC/DC

CONVERTER

RX2

100Ω

QRST

Si1012R

CBRST

R1

100k

CIRCUIT BREAKER

RESET CONTROL

RB1

243k

1%

RA1

49.9k

1%

RSENSE

WSL1206

0.05Ω, 1%

CD0

0.1µF

25V

Q0

Si2316DS

RG0

10Ω

CD1

0.1µF

25V

Q1

Si2316DS

RG1

10Ω

RB2

169k

1%

RA2

49.9k

1%

CBYP

10µF

25V

CD2

0.1µF

25V

15

14

1

VCC SENSE 13

2

V1

V2

GATE

3 V3 LTC2921

4 V4

12

PG

9

7

S1

5

S2

S3

GND

11

10

D1 8

D2

D3

6

TIMER

16 CTIMER

0.22µF

10V

Q2

Si2316DS

RG2

10Ω

CGATE

0.47µF

25V

Figure 12. Design Example of a Three-Supply Tracker and Monitor (5V, 3.3V, 2.5V)

5V

LOAD

0.8A MAX

3.3V

LOAD

1.6A MAX

2.5V

LOAD

0.4A MAX

R2

4.7k

RESET

2921/22 F12

Selecting RB1 = 243k satisfies the range restrictions be-

low:

RB1(MAX)

=

49.9k

•



1–

1+

00..0011

•





3.0525V – 0.505V

0.505V + 0.1µA • 49.9k





=

244.3k

RB1(MIN)

=

49.9k

•



1+

1–

00..0011

•





3.5475V + 0.250V – 0.665V

0.665V – 0.1µA • 49.9k 

=

241.6k

RA2

=

0.500V

10µA

=

50k

≈

49.9k

RB2(MAX)

=

49.9k

•



1–

1+

00..0011

•





2.3125V – 0.505V 

0.505V + 0.1µA • 49.9k

=

173.3k

RB2(MIN)

=

49.9k

•



1+

1–

00..0011

•





2.6875V + 0.150V

0.665V – 0.1µA

– 0.665V

• 49.9k 

=

167.6k

Similar calculations for the 2.5V supply yield suitable Tie the unused V3 and V4 monitor pins to V2 for proper

standard 1% values of RA2 = 49.9k and RB2 = 169k.

operation.

29212fa

16

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