LTC1657 View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTC1657

Parallel 16-Bit Rail-to-Rail Micropower DAC

Linear Technology 

LTC1657/LTC1657L

TYPICAL APPLICATIO S

This circuit shows a digitally programmable current source

from an external voltage source using an external op amp,

an LT1218 and an NPN transistor (2N3440). Any digital

word from 0 to 65535 is loaded into the LTC1657 and its

output correspondingly swings from 0V to 4.096V. This

voltage will be forced across the resistor RA. If RA is

chosen to be 412Ω, the output current will range from

0mA at zero scale to 10mA at full scale. The minimum

voltage for VS is determined by the load resistor RL and

Q1’s VCESAT voltage. With a load resistor of 50Ω, the

voltage source can be 5V.

Digitally Programmable Current Source

5V

22

23

5:19 DATA (0:15) REFHI REFOUT VCC

0.1µF

2

CSLSB

3

µP

CSMSB

1

WR

LTC1657

25

VOUT

3+

7

28 LDAC

LT1218

27

CLR X1/X2 REFLO GND

2–

4

26 21 20

5V < VS < 100V

FOR RL ≤ 50Ω

RL

IOUT

=

(DIN)(4.096)

(65536)(RA)

6

Q1

≈ 0mA TO 10mA

2N3440

RA

412Ω

1%

1657 TA04

13

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