MAX5150 Maxim, MAX5150 Datasheet - Page 9

• Manufacturer Part Number: MAX5150
• Description: Low-Power / Dual / 13-Bit Voltage-Output DACs with Serial Interface
• Manufacturer: Maxim

The MAX5150/MAX5151 dual, 13-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 +2 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 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, 13-Bit Voltage-Output DACs
NAME
DGND
DOUT
AGND
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
Clears all DACs and registers
(resets to 0).
Chip-Select Input
Serial-Data Input
Serial-Register 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 8191) and V
age.
The reference input impedance ranges from 14kΩ
(1555 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 an input code of all
ones.
The output amplifiers on the MAX5150/MAX5151 have
internal resistors that provide for a gain of +2 when OS_
is connected to AGND. These resistors are trimmed to
minimize gain error. The output amplifiers have a typi-
cal slew rate of 0.75V/µs and settle to 1/2LSB within
16µs, 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 MAX5150/MAX5151 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
Figure 1. Simplified DAC Circuit Diagram
AGND
REF_
SHOWN FOR ALL 1s ON DAC
with Serial Interface
2R
V
2R
OUT
D0
R
= (V
REF
2R
D10
R
REF
x NB / 8192) x 2
REF
x 2). Note that the DAC’s
2R
D11
Power-Down Mode
R
Output Amplifier
is the reference volt-
and amplifier out-
2R
D12
R
R
OS_
OUT_
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