MAX5158 Maxim, MAX5158 Datasheet - Page 9

• Manufacturer Part Number: MAX5158
• Description: Low-Power / Dual / 10-Bit / Voltage-Output DACs with Serial Interface
• Manufacturer: Maxim

The MAX5158/MAX5159 dual, 10-bit, voltage-output
DACs are easily configured with a 3-wire serial inter-
face. These devices include 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 maxi-
mizes 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 0V to (V
Determine the output voltage using the following equa-
tion (OS_ = AGND):
_____________________Pin Description
_______________Detailed Description
PIN
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
Low-Power, Dual, 10-Bit, Voltage-Output DACs
NAME
AGND
DGND
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 1023) and V
The reference input impedance ranges from 18kΩ
(1558 hex) to several giga ohms (with an input code of
0000 hex). The reference input capacitance is code
dependent and typically ranges from 15pF with an
input code of all zeros to 50pF with a full-scale input
code.
The output amplifiers on the MAX5158/MAX5159 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 8µs, 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 volt-
age specification.
The MAX5158/MAX5159 feature a software-program-
mable shutdown mode that reduces the typical supply
current to 2µA. The two DACs can be shutdown inde-
pendently, or simultaneously using the appropriate pro-
gramming command. Enter shutdown mode by writing
the appropriate input-control word (Table 1). In shut-
down mode, the reference inputs
puts become high impedance, and the serial interface
Figure 1. Simplified DAC Circuit Diagram
AGND
REF_
SHOWN FOR ALL 1s ON DAC
with Serial Interface
2R
V
2R
D0
OUT
R
= (V
REF
REF
2R
D7
R
REF
is the reference voltage.
x NB / 1024) x 2
x 2). Note that the DAC’s
2R
D8
Power-Down Mode
R
Output Amplifier
and amplifier out-
2R
D9
R
R
OUT_
OS_
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