MAX5188BEEI MAXIM [Maxim Integrated Products], MAX5188BEEI Datasheet - Page 8

• Manufacturer Part Number: MAX5188BEEI
• Description: Dual, 8-Bit, 40MHz, Current/Voltage, Alternate-Phase Output DACs
• Manufacturer: MAXIM [Maxim Integrated Products]

Dual, 8-Bit, 40MHz, Current/Voltage,
Alternate-Phase Output DACs
Figure 1. Functional Diagram
The MAX5188/MAX5191 are dual 8-bit digital-to-analog
converters (DACs) capable of operating with clock
speeds up to 40MHz. Each of these dual converters
consists of separate input and DAC registers, followed
by a current-source array capable of generating up to
1.5mA full-scale output current (Figure 1). An integrat-
ed +1.2V voltage reference and control amplifier deter-
mine the data converters’ full-scale output currents/
voltages. Careful reference design ensures close gain
matching and excellent drift characteristics. The
MAX5191’s voltage output operation features matched
400Ω on-chip resistors that convert the current from the
current array into a voltage.
The MAX5188/MAX5191 provide an integrated
50ppm/°C, +1.2V, low-noise bandgap reference that
can be disabled and overridden by an external refer-
ence voltage. REFO serves either as an input for an
external reference or as an output for the integrated ref-
erence. If REN is connected to DGND, the internal ref-
erence is selected and REFO provides a +1.2V output.
8
*INTERNAL 400Ω AND 9.6kΩ RESISTORS FOR MAX5191 ONLY.
_______________________________________________________________________________________
Detailed Description
REFO
REFR
CLK
and Control Amplifier
9.6k*
Internal Reference
1.2V REF
REN
MSB DECODE
LATCHES
LATCHES
OUTPUT
INPUT
AV
DAC 1 SWITCHES
DAC 2 SWITCHES
DD
D7–D0
SOURCE ARRAY
CURRENT-
Due to its limited 10µA output drive capability, the
REFO pin must be buffered with an external amplifier if
heavier loading is required.
The MAX5188/MAX5191 also employ a control amplifi-
er, designed to simultaneously regulate the full-scale
output current I
The output current is calculated as follows:
where I
V
R
amplifier’s output current (Figure 2) on the MAX5188.
This current is mirrored into the current-source array,
where it is equally distributed between matched current
segments and summed to valid output current readings
for the DACs.
Inside the MAX5191, each output current (DAC1 and
DAC2) is converted to an output voltage (V
V
resistors. Using the internal +1.2V reference voltage,
the integrated reference output current resistor of the
MAX5191 (R
1mA.
AGND
MSB DECODE
LATCHES
LATCHES
REFO
OUT2
OUTPUT
SET
INPUT
is the reference resistor that determines the
) with two internal, ground-referenced, 400Ω load
/ R
REF
CS
SET
SET
is the reference output current (I
) and I
DACEN
FS
= 9.6kΩ) sets I
DV
MAX5188
MAX5191
for both MAX5188/MAX5191 outputs.
DD
I
FS
FS
PD
= 8 · I
DGND
is the full-scale output current.
REF
OUT1P
OUT1N
OUT2P
OUT2N
CREF1
CREF2
REF
to 125µA and I
REF
OUT1
FS
to
=
,