DAC8512 Datasheet, PDF (5/20 Pages) Analog Devices – % V, Serial Input Complete 12-Bit DAC

DAC8512
PIN CONFIGURATIONS
SO-8
P-DIP-8 & Cerdip-8
VDD ₁
8 ^VOUT
CS 2 DAC8512 7 ^GND
CLK 3 ^{TOP VIEW} 6 CLR
(Not to Scale)
SDI 4
5 LD
VDD 1
CS 2
CLK 3
SDI 4
DAC8512
TOP VIEW
(Not to Scale)
8 V_OUT
7 GND
6 CLR
5 LD
PIN DESCRIPTIONS
Pin Name Description
1 V_DD Positive Supply. Nominal value +5 V, ± 5%.
2 CS Chip Select. Active low input.
3 CLK Clock input for the internal serial input shift register.
4 SDI Serial Data Input. Data on this pin is clocked into the
internal serial register on positive clock edges of the
CLK pin. The Most Significant Bit (MSB) is loaded
first.
5
LD Active low input which writes the serial register data
into the DAC register. Asynchronous input.
6
CLR Active low digital input that clears the DAC register to
zero, setting the DAC to minimum scale. Asynchronous
input.
7
GND Analog ground for the DAC. This also serves as the
digital logic ground reference voltage.
8
V_OUT Voltage output from the DAC. Fixed output voltage
range of 0 V to 4.095 V with 1 mV/LSB. An internal
temperature stabilized reference maintains a fixed
full-scale voltage independent of time, temperature and
power supply variations.
DICE CHARACTERISTICS
V_DD
1
V_OUT
8
7 GND
7 GND
6 CLR
CS 2
CLK ³
4
5
SDI
LD
SUBSTRATE IS COMMON WITH V_DD.
NUMBER OF TRANSISTORS : 642
DIE SIZE: 0.055 inch × 0.106 inch; 5830 sq mils
OPERATION
The DAC8512 is a complete ready to use 12-bit digital-to-analog
converter. It contains a voltage-switched, 12-bit, laser-trimmed
DAC, a curvature-corrected bandgap reference, a rail-to-rail
output op amp, a DAC register, and a serial data input register.
The serial data interface consists of a CLK, serial data in (SDI),
and a load strobe (LD). This basic 3-wire interface offers maxi-
mum flexibility for interface to the widest variety of serial data
input loading requirements. In addition a CS select is provided
for multiple packaging loading and a power on reset CLR pin to
simplify start or periodic resets.
D/A CONVERTER SECTION
The DAC is a 12-bit voltage mode device with an output that
swings from GND potential to the 2.5 volt internal bandgap
voltage. It uses a laser trimmed R-2R ladder which is switched
by N channel MOSFETs. The output voltage of the DAC has a
constant resistance independent of digital input code. The DAC
output is internally connected to the rail-to-rail output op amp.
AMPLIFIER SECTION
The DAC’s output is buffered by a low power consumption pre-
cision amplifier. This amplifier contains a differential PNP pair
input stage which provides low offset voltage and low noise, as
well as the ability to amplify the zero-scale DAC output volt-
ages. The rail-to-rail amplifier is configured in a gain of 1.6384
(= 4.095 V/2.5 V) in order to set the 4.095 volt full-scale output
(1 mV/LSB). See Figure 3 for an equivalent circuit schematic of
the analog section.
BANDGAP
REFERENCE
VOLTAGE SWITCHED 12-BIT
R-2R D/A CONVERTER
2R
RAIL-TO-RAIL
OUTPUT
AMPLIFIER
BUFFER
2.5V
R
2R
R
2R
R2
R1
VOUT
AV = 4.095/2.5
= 1.638V/V
2R
SPDT
N-CH FET
SWITCHES
2R
Figure 3. Equivalent DAC8512 Schematic of Analog
Portion
The op amp has a 16 µs typical settling time to 0.01%. There
are slight differences in settling time for negative slowing signals
vs. positive. See the oscilloscope photos in the typical perfor-
mances section of this data sheet.
REV. A
–5–