X96012 Datasheet, PDF (18/27 Pages) Intersil Corporation – Universal Sensor Conditioner with Dual Look Up Table Memory and DACs

X96012
By examining the block diagram in Figure 8, we see
that the maximum current through pin I1 is set by fixing
values for V(VRef) and R1. The output current can
then be varied by changing the data byte at the D/A
converter input.
In general, the magnitude of the current at the D/A
converter output pins (I1, I2) may be calculated by:
Ix = (V(VRef) / (384 • Rx)) • N
where x = 1,2 and N is the decimal representation of
the input byte to the corresponding D/A converter.
The value for the resistor Rx (x = 1,2) determines the
full scale output current that the D/A converter may sink
or source. The full scale output current has a maximum
value of ±3.2 mA, which is obtained using a resistance
of 255Ω for Rx. This resistance may be connected
externally to pin Rx of the X96012, or may be selected
from one of three internal values. Bits I1FSO1 and
I1FSO0 select the full scale output current setting for I1
as described in “I1FSO1 - I1FSO0: Current Generator
1 Full Scale Output Set Bits (Non-volatile)” on
page 13. Bits I2FSO1 and I2FSO0 select the maximum
current setting for I2. When an internal resistor is
selected for R1 or R2, then no resistor should be con-
nected externally at the corresponding pin.
Figure 10. Look-Up Table Addressing
Voltage
Reference
Voltage Input
ADC
6
8
AD[7:0]
Status
Register
Bits I1DS and I2DS in Control Register 0 select the
direction of the currents through pins I1 and I2 inde-
pendently (See “I1DS: Current Generator 1 Direction
Select Bit (Non-volatile)” on page 11 and “Control and
Status Register Format” on page 12).
D/A Converter Output Current Response
When the D/A converter input data byte changes by
an arbitrary number of bits, the output current changes
from an intial current level (I_x) to some final level
(I_x + ∆I_x). The transition is monotonic and glitchless.
D/A Converter Control
The data byte inputs of the D/A converters can be con-
trolled in three ways:
– 1) With the A/D converter and through the look-up
tables (default),
– 2) Bypassing the A/D converter and directly access-
ing the look-up tables,
– 3) Bypassing both the A/D converter and look-up tables,
and directly setting the D/A converter input byte.
L2DA[5:0]:
Control
Register 2
D1
Out
D0
Select
LUT2 Row
Selection bits
L2DAS: bit 6 in
Control register 5
L1DA[5:0]:
Control
6
D1
Register 1
Out
D0
Select
LUT1 Row
Selection bits
L1DAS: bit 4 in
Control register 5
18
FN8216.0
March 10, 2005