Table 1. power-down mode selection – Rainbow Electronics MAX5191 User Manual
Page 9
MAX5188/MAX5191
Dual, 8-Bit, 40MHz, Current/Voltage,
Alternate-Phase Output DACs
_______________________________________________________________________________________
9
External Reference
To disable the MAX5188/MAX5191’s internal reference,
connect REN to DV
DD
. A temperature-stable external
reference may now be applied to drive the REFO pin
(Figure 3) to set the full-scale output. Choose a refer-
ence that can supply at least 150µA to drive the bias
circuit that generates the cascode current for the cur-
rent array. For improved accuracy and drift perfor-
mance, choose a fixed output voltage reference such
as the +1.2V, 25ppm/°C MAX6520 bandgap reference.
Standby Mode
To enter the lower-power standby mode, connect digi-
tal inputs PD and DACEN to DGND. In standby, both
the reference and the control amplifier are active with
the current array inactive. To exit this condition, DACEN
must be pulled high with PD held at DGND. The
MAX5188/MAX5191 typically require 50µs to wake up
and allow both the outputs and the reference to settle.
Shutdown Mode
For lowest power consumption, the MAX5188/MAX5191
provide a power-down mode in which the reference,
control amplifier, and current array are inactive and the
DAC’s supply current is reduced to 1µA. To enter this
mode, connect PD to DV
DD
. To return to active mode,
connect PD to DGND and DACEN to DV
DD
. About 50µs
are required for the devices to leave shutdown mode
and settle their outputs to the values prior to shutdown.
Table 1 lists the power-down mode selection.
R
SET
**
9.6k
I
FS
R
SET
C
COMP
*
REFR
I
REF
REFO
MAX4040
+1.2V
BANDGAP
REFERENCE
CURRENT-
SOURCE ARRAY
*COMPENSATION CAPACITOR (C
COMP
= 100nF)
**9.6k
Ω REFERENCE CURRENT SET RESISTOR
INTERNAL TO MAX5191 ONLY. USE EXTERNAL
R
SET
FOR MAX5188.
OPTIONAL EXTERNAL BUFFER
FOR HEAVIER LOADS
REN
MAX5188
MAX5191
I
REF
=
V
REF
R
SET
AGND
AGND
DGND
Figure 2. Setting I
FS
with the Internal +1.2V Reference and Control Amplifier
Table 1. Power-Down Mode Selection
X = Don’t care
MAX5191
MAX5188
MAX5191
MAX5188
1
X
Shutdown
AGND
0
0
Standby
AGND
PD
(POWER-DOWN SELECT)
DACEN
(DAC ENABLE)
POWER-DOWN
MODE
OUTPUT STATE
High-Z
0
1
Wake-Up
Last state prior to standby mode
High-Z