Philips Semiconductors Linear Products

Product specification

AM6012

12-Bit multiplying D/A converter

August 31, 1994

782

FREQUENCY MHz

Figure 2.

REFERENCE CONFIGURATION

Positive reference

0V

N/C

0.01

µF

Negative reference

0V

N/C

0.01

µF

Lo impedance bipolar reference

0V

Hi impedance bipolar reference

0V

No Cap

NOTES:

1.

The compensation capacitor is a function of the impedance seen at the +VREF input and must be at least 5pF x R14(eq) in kΩ. For R14 < 800Ω no capacitor is necessary.

2.

For negative values of VIN, VR+ / R14 must be greater than –VIN max / RIN so that the amplifier is not turned off.

3.

For positive values of VIN, VR+ must be greater than –VIN max so the amplifier is not turned off.

4.

For pulsed operation, VR+ provides a DC offset and may be set to zero in some cases. The impedance at Pin 14 should be 800Ω or less.

5.

For optimum settling time, decouple V– with 20

Ω and bypass with 22µF tantalum capacitor.

6.

Reference current and reference resistor — there is a 1-to-4 scale factor between the reference current (IREF) and the full-scale output current (IFS).

If VREF = +10V and IFS = 4mA, the value of the R14 is:

R

14 +

4

x 10V

4

mA

+ 10kW

R

14 +

R

15

a. Reference Amplifier Biasing

b.

Reference Amplifier

Frequency Response

Minimum Size

Compensation Capacitor

(IFS = 4mA, IREF = 1.0mA)

R14(EQ) (kΩ)

CC (pF)

10

5

2

1

.5

50

25

10

5

0

NOTE:

A 0.01

µF capacitor is recommended for fixed

reference operation.

14

15

REFERENCE

AMPLIFIER

AM6012

18

19

FOR ALL INPUT CODES

COMP

0.1

20

(NOTE 5)

IO + IO = IFS

IO

IO

V–

V+

V–

I15

IREF

VIN

RIN

R14

R15

VR+

VR–

22

µF TANTALUM

R15 = R14 = RIN

VIN

CC

0.1

6

4

2

0

–2

–4

–6

–8

.01

0.1

1.0

10

LARGE SIGNAL = 50%

MODULATION OF 4mA

FULL SCALE CURRENT

SMALL SIGNAL = 1%

MODULATION OF 2mA

FULL SCALE CURRENT

R14 (EQ) = 2kΩ

CC = 10pF