ISL24212_14 Datasheet, PDF (8/12 Pages) Intersil Corporation – Programmable VCOM Calibrator with EEPROM and Output Buffer

ISL24212
By finding the difference of Equation 13 and Equation 12, the total
span of V_COM can be found:
V_COMSPAN
=
A
V_D
D
⎛
⎜
⎝
--_R----₁-^R--+--²--_R-----₂--_{⎠⎟⎞}
⎛
⎝
1
–
2^----51^----6^{- ⎠⎞}
⎛
⎜
⎝
2^----0^---R-R^---1-_S^----_E^---_T^-_{⎠⎟⎞}
(EQ. 14)
Assuming that the I_DVROUT(MIN) = 0 instead of I_STEP, the
expression in Equation 14 simplifies to:
V_COMSPAN
=
⎛
⎜
⎝
R^-R----₁^{-1---+-⋅---R-}R^---2-₂^--_{⎠⎟⎞}
⎛
⎜
⎝
2^{----A0----VR---D-}_S^---DE----_T^-_{⎠⎟⎞}
=
⎛
⎜
⎝
R^-R----₁^{-1---+-⋅---R-}R^---2-₂^--_{⎠⎟⎞}
I_DV
RO
U
T⁽
M
A
X)
(EQ. 15)
DVR_OUT Pin Leakage Current
When the voltage on the DVR_OUT pin is greater than 10V, an
additional leakage current flows into the pin in addition to the
I_SET current. Figure 6 shows the I_SET current and the DVR_OUT
pin current for DVR_OUT pin voltage up to 19V. In applications
where the voltage on the DVR_OUT pin will be greater than 10V,
the actual output voltage will be lower than the voltage
calculated by Equation 8 due to this extra current. The graph in
Figure 6 was measured with R_SET = 4.99kΩ.
0.30
REGISTER = 255
0.25
OUT PIN CURRENT
0.20
SET PIN CURRENT
0.15
0.10
0.05
0.00
0 2 4 6 8 10 12 14 16 18 20
OUT PIN VOLTAGE (V)
FIGURE 6. DVR_OUT PIN LEAKAGE CURRENT
Power Supply Sequence
The recommended power supply sequencing is shown in
Figure 7. When applying power, V_DD should be applied before or
at the same time as AV_DD. The minimum time for t_VS is 0µs.
When removing power, the sequence of V_DD and AV_DD is not
important.
V_DD
A_VDD
t_VS
FIGURE 7. POWER SUPPLY SEQUENCE
Do not remove V_DD or AV_DD within 100ms of the start of the
EEPROM programming cycle. Removing power before the
EEPROM programming cycle is completed, may result in
corrupted data in the EEPROM.
Operating and Programming
Supply Voltage and Current
To program the EEPROM, AV_DD must be ≥10.8V. If further
programming is not required, the ISL24212 will operate over an
AV_DD range of 4.5V to 19V.
During EEPROM programming, I_DD and I_AVDD will temporarily be
4-5x higher for up to 100ms (t_PROG).
Up/Down Counter Interface
The ISL24212 allows the adjustment of the output V_COM voltage
and the programming of the non-volatile memory through a
single pin (CTL) when the CE (counter enable) pin is high. The CTL
pin is biased so that its voltage is set to VDD/2 if the driving
circuit is set to Tristate or High Impedance (Hi-Z), allowing
up/down operation using common digital I/O logic.
CTL Pin
When a mid-high-mid transition is detected on the CTL pin (see
Figure 11), the internal register value counts down by one at the
trailing (high-mid) edge, and the output V_COM voltage is
increased according to Equation 8. Similarly, when a mid-low-mid
transition is detected on the CTL pin, the internal register value
counts up by one at the trailing (low-mid) edge, and the output
V_COM voltage is decreased. Once the maximum or minimum
value is reached, the counter saturates and will not overflow or
underflow beyond those values.
CTL should have a noise filter to reduce bouncing or noise on the
input that could cause unwanted counts when the CE pin is high.
Figure 8 shows a simple debouncing circuit consisting of a series
1kΩ resistor and a shunt 0.01µF capacitor connected on the CTL
pin. To avoid unintentional adjustment, the ISL24212 guarantees
to reject CTL pulses shorter than 20µs.
AV_DD
CLOSE TO
PROGRAM
EEPROM
ISL24212
1kΩ
CTL
0.01µF
FIGURE 8. EXTERNAL DEBOUNCER ON CTL PIN
This pin is pulled above 4.9V to program the EEPROM. See
“Programming the EEPROM” on page 9 for details.
After CE (Counter Enable) is asserted and after programming
EEPROM, the very first CTL pulse is ignored (see Figure 11) to
avoid the possibility of a false count (CTL state may be unknown
after programming).
8
FN7590.0
March 15, 2011