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Detailed Description
The HI1171 is an 8-bit, current out D/A converter. The DAC
can convert at 40MHz and run on a single +5V supply. The
architecture
is
an
encoded,
switched
current
cell
arrangement.
Voltage Output Mode
The output current of the HI1171 can be converted into a volt-
age by connecting an external resistor to IOUT1. To calculate
the output resistor use the following equation:
ROUT = VFS /IFS,
where VFS can range from +0.5V to +2.0V and IFS can
range from 0mA to 15mA.
In setting the output current the IREF pin should have a resistor
connected to it that is 16 times greater than the output resistor:
RREF = 16 x ROUT
As the values of both ROUT and RREF increase, power
consumption is decreased, but glitch energy and output
settling time is increased.
Clock Phase Relationship
The internal latch is closed when the clock line is high. The
latch can be cleared by the BLNK line. When BLNK is set
(HIGH) the contents of the internal data latch will be cleared.
When BLNK is low data is updated by the CLK.
Noise Reduction
To reduce power supply noise separate analog and digital
power supplies should be used with 0.1
F ceramic capaci-
tors placed as close to the body of the HI1171 as possible.
The analog (AVSS) and digital (DVSS) ground returns should
be connected together back at the power supply to ensure
proper operation from power up.
17
VG
Voltage Ground, connect a 0.1
F capacitor to AV
DD.
18, 19, 22
AVDD
Analog Supply 4.75V to 7V.
20
IOUT1
Current Output Pin.
21
IOUT2
Current Output pin used for a virtual ground connection. Usually connected to AVSS.
23, 24
DVDD
Digital Supply 4.75V to 7V.
Pin Descriptions (Continued)
24 PIN
SOIC
PIN
NAME
PIN DESCRIPTION
Test Circuits
FIGURE 5. MAXIMUM CONVERSION SPEED TEST CIRCUIT
OSCILLOSCOPE
8-BIT
WITH LATCH
CLK
40MHz
SQUARE WAVE
COUNTER
1
2
8
9
11
12
15
16
17
20
CLK
VB
0.1
F
BLK
D7
(LSB) D0
IO
VG
VREF
2V
IREF
AVDD
1k
AVSS
3.3k
200
0.1
F
HI1171