Datasheet
AD7804/AD7805/AD7808/AD7809
–7–REV. A
AD7804/AD7808 PIN FUNCTION DESCRIPTION
AD7804 AD7808
Pin No. Pin No. Mnemonic Description
1 1, 6 AGND Ground reference point for analog circuitry.
2, 3 2, 3 V
OUT
B, V
OUT
A Analog output voltage from the DACs.
4 4 REFOUT Reference Output. This is a bandgap reference and is typically 1.23 V.
5 PD Active low input used to put the part into low power mode reducing current consumption
to 1 µA.
7, 8 V
OUT
F, V
OUT
E Analog output voltages from the DACs.
59FSIN Level-triggered control input (active low). This is the frame synchronization signal for the
input data. When FSIN goes low, it enables the input shift register and data is transferred
on the falling edges of CLKIN.
610LDAC LDAC Input. When this digital input is taken low, all DAC registers are simultaneously
updated with the contents of the data registers. If LDAC is tied permanently low, or is
low on the sixteenth falling clock edge with timing similar to that of SDIN, an automatic
update will take place.
7 11 SDIN Serial Data Input. These devices accept a 16-bit word. Data is clocked into the input shift
register on the falling edge of CLKIN.
8 12 DGND Ground reference point for digital circuitry.
913DV
DD
Digital Power Supply.
10 14 CLKIN Clock Input. Data is clocked into the input shift register on the falling edges of CLKIN.
Duty Cycle should be between 40% and 60%.
11 15 CLR Asynchronous CLR Input. When this input is taken low, all Main DAC outputs are
cleared either to V
BIAS
or to V
BIAS
/16 volts. All Sub DACs are also cleared and thus the
transfer function of the Main DAC will remain centered around the V
BIAS
point.
16 NC No Connect. This pin should be left open circuit.
17, 18 V
OUT
H, V
OUT
G Analog output voltages from the DACs.
12 20 REFIN This is an external reference input for the DACs. When this reference is selected for a
DAC in the control register, the analog output from the selected DAC swings around this
point.
13 21 COMP Compensation Pin. This pin provides an output from the internal V
DD
/2 divider and is
provided for ac bypass purposes only. This pin should be decoupled with 1 nF capacitors
to both AV
DD
and AGND. This pin can be overdriven with an external reference, thus
giving the facility for two external references on the part.
14, 15 22, 23 V
OUT
D, V
OUT
C Analog output voltage from the DACs.
16 19, 24 AV
DD
Analog Power Supply. +3.3 V to +5 V.
AD7804 PIN CONFIGURATION
TOP VIEW
(Not to Scale)
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
AGND
V
OUT
B
V
OUT
A
REFOUT
FSIN
LDAC
SDIN
DGND
AV
DD
V
OUT
C
V
OUT
D
COMP
REFIN
CLR
CLKIN
DV
DD
AD7804
AD7808 PIN CONFIGURATION
TOP VIEW
(Not to Scale)
24
23
22
21
20
19
18
17
16
15
14
13
1
2
3
4
5
6
7
8
9
10
11
12
AD7808
NC = NO CONNECT
DGND
SDIN
LDAC
FSIN
V
OUT
E
AGND
V
OUT
B
V
OUT
A
REFOUT
V
OUT
F
AGND
PD
DV
DD
CLKIN
CLR
NC
V
OUT
H
AV
DD
V
OUT
C
V
OUT
D
COMP
V
OUT
G
AV
DD
REFIN