AD8804_15 Datasheet, PDF (14/16 Pages) Analog Devices – 12 Channel, 8-Bit TrimDACs with Power Shutdown

AD8802/AD8804
P0.0
USER
INPUTS
P0.7
P3.2
P3.1
P3.0
P3.3
80CL51 µC
P1.0/INT2
P2.0
P2.1
P2.2
P2.3
P2.4
AD8802/4 ^VREFH
CS
CLK
SDI
3
TO 2nd AD8802/4
ARRAY IF NEEDED
O1
O2
O3
O4
4
05–8
4
09–12
TO 2nd TEMP SENSOR
IF NEEDED
TO 3rd TEMP SENSOR
IF NEEDED
SHDN
V_DD
GND
0.1µF
+5V
10µF
+5V
0.01µF
V_CC RS
TLC555 ^DIS
3 _OUT
THR
GND ^TRIG
TMP14
2.5 V_REF
SET 1
SET 2
SET 3
SET 4
HYS
TRIP 1
TRIP 2
TRIP 3
TRIP 4
V+
SLEEP
GND
+5V
0.1µF
Figure 27. Temperature Sensor Array with Programmable Setpoints
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.)
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
18kΩ
50pF
VOUT
1
16
+15V
2 _SSM2018T 15
3
4
1µF _18kΩ
5
6
14
13
R_O
150kΩ
12
11
7
1µF ^18kΩ
8
47pF
10
9 NC
–15V
+V
TO 8 MORE CHANNELS
O2
O3
O4–O12
OPTIONAL FOR
0 TO 40dB GAIN
+15V
1.2V
50kΩ
OP420A
AD8802/4
O1
V_REFH
O2–
O12
CS
CLK
SDI
3
V_REFL
(AD8804
ONLY)
V+
GND
TO µC
REF195
OUT IN
+15V
1µF
GND
Figure 28. 12-Channel Programmable Voltage Controlled Amplifier
–14–
REV. 0