DAC7724
DAC7725
+10.000V
–10.000V
0.1µF
–10V to +10V
–10V to +10V
0.1µF
–10V to +10V
–10V to +10V
+15V
+
1
2
3
4
5
6
7
8
9
VREFH
VOUTB
VOUTA
VSS
VREFL 28
VOUTC 27
VOUTD 26
VCC 25
VDD 24
CS 23
0.1µF
0.1µF
1µF to 10µF
–15V
+5V
+
1µF to 10µF
0.1µF
+
GND
RESET
LDAC
DB0
1µF to 10µF
Reset DACs(1)
Chip Select
Load DAC Registers
A0 22
Address Bus
or Decoder
A1 21
Read/Write
DB1
R/W 20
DB11 19
DB10 18
DB9 17
DB8 16
DB7 15
10 DB2
11 DB3
12 DB4
13 DB5
14 DB6
Data Bus
Data Bus
NOTE: (1) Reset LOW sets all DACs to code 800H on the DAC7724 and to code 000H on the DAC7725.
FIGURE 3. Basic Dual-Supply Operation of the DAC7724/25.
ANALOG OUTPUTS
tially, the offset of the output op-amp). The maximum
output is equal to VREFH plus a similar offset voltage. Note
that VSS (the negative power supply) must either be con-
nected to ground or must be in the range of –14.25V to
–15.75V. The voltage on VSS sets several bias points within
the converter, if VSS is not in one of these two configura-
tions, the bias values may be in error and proper operation
of the device is not guaranteed.
When VSS = –15V (dual supply operation), the output
amplifier can swing to within 4V of the supply rails, guar-
anteed over the –40°C to +85°C temperature range. With
VSS = 0V (single-supply operation) and RLOAD connected to
ground, the output can swing to ground. Note that the
settling time of the output op-amp will be longer with
voltages very near ground. Additionally, care must be taken
when measuring the zero-scale error when VSS = 0V. Since
the output voltage cannot swing below ground, the output
voltage may not change for the first few digital input codes
(000H, 001H, 002H, etc.) if the output amplifier has a nega-
tive offset. At the negative offset limit of –4 LSB (-9.76mV),
for the single-supply case, the first specified output starts at
code 004H.
The current into the VREFH input and out of VREFL depends
on the DAC output voltages and can vary from a few
microamps to approximately 0.3mA. The reference input
appears as a varying load to the reference. If the reference
can sink or source the required current, a reference buffer is
not required. See “Reference Current vs Code” in the Typi-
cal Performance Curves.
The analog supplies (or the analog supplies and the refer-
ence power supplies) have to come up first. If the power
supplies for the references come up first, then the VCC and
VSS supplies will be “powered from the reference via the
ESD protection diodes” (see page 4).
REFERENCE INPUTS
For dual-supply operation, the reference inputs, VREFL and
VREFH, can be any voltage between VSS + 4V and VCC – 4V
provided that VREFH is at least 1.25V greater than VREFL
.
For single-supply operation (VSS = 0V), VREFL value can be
above 0V, with the same provision that VREFH is at least
1.25V greater than VREFL. The minimum output of each
DAC is equal to VREFL plus a small offset voltage (essen-
Bypassing the reference voltage or voltages with at least a
0.1uF capacitor placed as close to the DAC7724/25 package
is strongly recommended.
®
13
DAC7724, 7725
BB [ BURR-BROWN CORPORATION ]
