MAX5122 Maxim, MAX5122 Datasheet - Page 10

• Manufacturer Part Number: MAX5122
• Description: +5V/+3V / 12-Bit / Serial / Force/Sense DACs with 10ppm/C Internal Reference
• Manufacturer: Maxim

The MAX5122/MAX5123 12-bit, force/sense DACs are
easily configured with a 3-wire serial interface. They
include a 16-bit data-in/data-out shift register and have
a double-buffered digital input consisting of an input
register and a DAC register. In addition, these devices
employ precision bandgap references, as well as an
output amplifier with accessible feedback and output
pins that can be used to set the gain externally (Figure
1) or for forcing and sensing applications. These DACs
are designed with an inverted R-2R ladder network
(Figure 2) that produces a weighted voltage proportion-
al to the digital input code.
Both devices use an on-board precision bandgap ref-
erence with a low temperature coefficient of only
10ppm/°C (max) to generate an output voltage of +2.5V
(MAX5122) or +1.25V (MAX5123). The REF pin can
source up to 100µA and may become unstable with
capacitive loads exceeding 100pF. REFADJ can be
used for minor adjustments to the reference voltage.
+5V/+3V, 12-Bit, Serial, Force/Sense DACs
with 10ppm/°C Internal Reference
Figure 1. Simplified Functional Diagram
10
_______________Detailed Description
______________________________________________________________________________________
RSTVAL
PDL
CLR
PD
( ) ARE FOR MAX5123 ONLY.
CS
REFERENCE
BANDGAP
CONTROL
Internal Reference
DIN SCLK
SR
MAX5122
MAX5123
1.25V
4k
12
REFADJ
SHIFT REGISTER
16-BIT
V
(X1)
REGISTER
2X
DD
INPUT
REFERENCE
AGND DGND
BUFFER
CONTROL
2.5V (1.25V)
DECODE
Figure 2. Simplified Inverted R-2R DAC Structure
AGND
REF*
NOTE: SHOWN FOR ALL 1s ON DAC.
REGISTER
DAC
2R
2R
D0
R
DAC
REF
OUTPUT
LOGIC
2R
D9
R
*INTERNAL REFERENCE: +2.5V (MAX5122),
+1.25V (MAX5123); OR EXTERNAL REFERENCE
2R
D10
R
DOUT
OUT
UPO
FB
2R
D11
FB
OUT