ISL22317 Datasheet, PDF (14/15 Pages) Intersil Corporation – Precision Single Digitally Controlled Potentiometer (XDCP™)

ISL22317
Rheostat Mode Configuration
When DCP is used as a two-terminal variable resistor, the
RH terminal should be left unconnected and MSR<7> is 0.
Resistance between RW and RL terminal can be calculated
by Equation 1:
Ri
=
R_-----t_--o_----t_--a_----l
127
×
i
(EQ. 1)
Where i is a decimal code from 0 to 127. Note, that
resistance accuracy will decrease at the lowest and the
highest taps, where voltage drops < 0.3V. In other words, a
minimum and maximum decimal code at which the DCP
resistance not exceed 3% precision is as shown in
Equations 2 and 3:
Voltage Divider Mode Configuration
In Voltage Divider Mode, voltage or signal is applied
between RH and RL terminals and MSR<7> is 1. A potential
at RH terminal must be higher than at RL terminal at any
time. Total resistance between RH and RL terminal is fixed
and matched to external reference resistor. Voltage on the
wiper terminal RW can be calculated by Equation 4:
Vrw(i)
=
V_-----r_--h_{-----–-----}V_----r_--l
127
×
i
(EQ. 4)
Where i is a decimal code from 0 to 127. Note, that the wiper
voltage accuracy will decrease at the lowest and the highest
taps, where it is less than 0.3V from ground or from V_CC
respectively.
i(min) = _I---_w----_i--_p0----^.e-³---_r--^×-_×----¹-_R--²---_t-⁷-_o----_t--_a----_l
(EQ. 2)
i(max) = ⁽--_I-^V--_w--^c--_i--^cp----_e^–----_r-⁰--_×-^.--³--_R--⁾---_t^×--_o---¹-_t--_a2----^7l-
(EQ. 3)
Where Iwiper is a current going through the wiper terminal.
Applications Information
In order to get better accuracy in applications where RL pin
is connected to GND, it is highly recommended that REF_B
pin is also connected to GND.
The coupling capacitors of 1µF and 0.1µF should be placed
close to VCC pin.
Revision History
DATE
5/26/09
REVISION
FN6912.0
CHANGE
Initial Release of Datasheet. Issued FN6912 making it a Rev 0.
14
FN6912.0
May 26, 2009