AD8802/AD8804

REV. 0

–14–

USER

INPUTS

3

TO 2nd AD8802/4

ARRAY IF NEEDED

TO 2nd TEMP SENSOR

IF NEEDED

4

TO 3rd TEMP SENSOR

IF NEEDED

4

0.1µF

10µF

+5V

+5V

0.1µF

TMP14

0.01µF

3

OUT

RS

DIS

THR

TRIG

GND

AD8802/4

TLC555

SET 1

SET 2

SET 3

SET 4

HYS

TRIP 1

TRIP 2

TRIP 3

TRIP 4

V+

GND

SLEEP

O1

O3

O4

O2

05–8

09–12

GND

SHDN

CS

CLK

SDI

P2.0

P2.1

P2.2

P2.3

P2.4

80CL51 µC

P1.0/INT2

P0.0

P0.7

P3.2

P3.1

P3.0

P3.3

+5V

Figure 27. Temperature Sensor Array with Programmable Setpoints

The gain of the SSM2018T is controlled by the voltage at Pin 11.

For maximum attenuation of –100 dB a control signal of 3.0 V

typ is necessary. The control signal has a scale of –30 mV/dB

centered around 0 dB gain for 0 V of control voltage, therefore,

for a maximum gain of 40 dB a control voltage of –1.2 volts is

necessary. Now notice that the normal +5 V to GND voltage

range of the AD8802/AD8804 does not cover the 3.0 V to

–1.2 V operational gain control range of the SSM2018T. To

cover the operating gain range fully and not exceed the maxi-

mum specified power supply rating requires the O1 output of

AD8802/AD8804 to be level shifted down. In Figure 28, the

level shifting is accomplished by a Zener diode and 1/4 of an

OP420 quad op amp. For applications that require only

TMP14, and makes the necessary adjustments to the AD8802/

AD8804 before shutting down again. The 80CL51 consumes

only 50

µA when operating at 32 kHz, in which case there

would be no need for the TLC555, which consumes 1 mW typ.

12 Channel Programmable Voltage Controlled Amplifier

The SSM2018T is a trimless Voltage Controlled Amplifier

(VCA) for volume control in audio systems. The SSM2018T is

the first professional quality audio VCA in the marketplace that

does not require an external trimming potentiometer to mini-

mize distortion. The TrimDAC shown in Figure 28 is not being

used to trim distortion, but rather to control the gain of the am-

plifier. In this configuration up to twelve SSM2018T can be

digitally controlled. (Please refer to the SSM2018T data sheet

for more specifications and applications information.)

–15V

150k

Ω

+V

50pF

18k

Ω

18k

Ω

1µF

18k

Ω

1µF

+15V

8

1

2

3

4

7

6

5

14

13

12

11

16

15

10

9

SSM2018T

OP420A

1.2V

+15V

50k

Ω

OPTIONAL FOR

0 TO 40dB GAIN

O1

O2–

O12

TO 8 MORE CHANNELS

O2

O3

O4–O12

CS

CLK

SDI

3

TO µC

1µF

(AD8804

ONLY)

OUT

IN

GND

REF195

V+

GND

+15V

AD8802/4

47pF

NC

Figure 28. 12-Channel Programmable Voltage Controlled Amplifier