max5104ceet Maxim Integrated Products, Inc., max5104ceet Datasheet - Page 6

• Manufacturer Part Number: max5104ceet
• Description: Max5104 Low-power, Dual, Voltage-output, 12-bit Dac With Serial Interface
• Manufacturer: Maxim Integrated Products, Inc.

The MAX5104 dual, 12-bit, voltage-output DAC is easily
configured with a 3-wire serial interface. The device
includes a 16-bit data-in/data-out shift register, and
each DAC has a double-buffered input composed of an
input register and a DAC register (see Functional
Diagram ). In addition, trimmed internal resistors produce
an internal gain of +2V/V that maximizes output voltage
swing. The amplifier’s offset-adjust pin allows for a DC
shift in the DAC’s output.
Both DACs use an inverted R-2R ladder network that
produces a weighted voltage proportional to the input
voltage value. Each DAC has its own reference input to
facilitate independent full-scale values. Figure 1 depicts
a simplified circuit diagram of one of the two DACs.
The reference inputs accept both AC and DC values
with a voltage range extending from 0 to (V
Determine the output voltage using the following equa-
tion (OS_ = AGND):
Low-Power, Dual, Voltage-Output, 12-Bit DAC
with Serial Interface
_____________________Pin Description
6
_______________Detailed Description
PIN
10
11
12
13
14
15
16
_______________________________________________________________________________________
1
2
3
4
5
6
7
8
9
NAME
DGND
AGND
DOUT
OUTA
OUTB
REFA
SCLK
REFB
OSA
UPO
OSB
PDL
V
DIN
CL
CS
DD
Analog Ground
DAC A Output Voltage
DAC A Offset Adjustment
Reference for DAC A
Active-Low Clear Input. Resets all reg-
isters to zero. DAC outputs go to 0V.
Chip-Select Input
Serial-Data Input
Serial-Clock Input
Digital Ground
Serial-Data Output
User-Programmable Output
Power-Down Lockout. The device can-
not be powered down when PDL is low.
Reference for DAC B
DAC B Offset Adjustment
DAC B Output Voltage
Positive Power Supply
FUNCTION
Reference Inputs
DD
- 1.4V).
where NB is the numeric value of the DAC’s binary input
code (0 to 4095) and V
The reference input impedance ranges from 14kΩ (1554
hex) to several gigohms (with an input code of 0000
hex). The reference input capacitance is code depen-
dent and typically ranges from 15pF with an input code
of all zeros to 50pF with a full-scale input code.
The MAX5104’s output amplifiers have internal resistors
that provide for a gain of +2V/V when OS_ is connected
to AGND. These resistors are trimmed to minimize gain
error. The output amplifiers have a typical slew rate of
0.75V/µs and settle to 1/2LSB within 15µs, with a load
of 10kΩ in parallel with 100pF. Loads less than 2kΩ
degrade performance.
The OS_ pin can be used to produce an adjustable off-
set voltage at the output. For instance, to achieve a 1V
offset, apply -1V to the OS_ pin to produce an output
range from 1V to (1V + V
output range is still limited by the maximum output voltage
specification.
The MAX5104 features a software-programmable shut-
down mode that reduces the typical supply current to
2µA. The two DACs can be powered down indepen-
dently, or simultaneously using the appropriate pro-
gramming command. Enter power-down mode by
writing the appropriate input-control word (Table 1). In
power-down mode, the reference inputs and amplifier
outputs become high impedance, and the serial inter-
face remains active. Data in the input registers is saved,
Figure 1. Simplified DAC Circuit Diagram
AGND
REF_
2R
V
OUT
2R
D0
R
= (V
REF
REF
2R
D10
· NB / 4096) · 2
R
REF
is the reference voltage.
· 2). Note that the DAC’s
2R
D11
Power-Down Mode
R
Output Amplifier
2R
D12
R
R
OS_
OUT_