10

LT1638/LT1639

proportional to the load current. As a convenient monitor,

the 2k load resistor converts the current into a voltage. The

the op amp and could be as high as 44V.

The Figure 4 application uses the LT1638 in conjunction

with the LT1634 micropower shunt reference. The supply

current of the op amp also biases the reference. The drop

across resistor R1 is fixed at 1.2V generating an output

current equal to 1.2V/R1.

–

+

1/2 LT1638

5V

200

Ω

200

Ω

0.2

Ω

2k

0V TO 4.3V

1638/39 F03

Q1

2N3904

LOAD

Figure 4. Current Source

Figure 3. Positive Supply Rail Current Sense

SI PLIFIED SCHE ATIC

Q10

D5

Q9

Q1

Q7

R2

1k

R3

1k

R4

8k

Q8

Q5

–IN

+IN

Q11

Q12

D4

ONE AMPLIFIER

D2

Q2

D1

Q6

Q13

Q14

R1

6k

R5

8k

Q4

10

µA

+

Q15

Q19

D3

Q3

Q16

Q18

Q22

Q17

Q20

Q21

OUT

1638/39 SS

MS8 Package

8-Lead Plastic MSOP

(LTC DWG # 05-08-1660)

MSOP (MS8) 1197

* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,

PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

0.021

± 0.006

(0.53

± 0.015)

0

° – 6° TYP

SEATING

PLANE

0.007

(0.18)

0.040

± 0.006

(1.02

± 0.15)

0.012

(0.30)

REF

0.006

± 0.004

(0.15

± 0.102)

0.034

± 0.004

(0.86

± 0.102)

0.0256

(0.65)

TYP

12

3

4

0.192

± 0.004

(4.88

± 0.10)

8

7 6

5

0.118

± 0.004*

(3.00

± 0.102)

0.118

± 0.004**

(3.00

± 0.102)

–

+

1/2 LT1638

R1

1.2V

R1

LT1634-1.2

1638/39 F04