ISL45042 Intersil Corporation, ISL45042 Datasheet - Page 6

• Manufacturer Part Number: ISL45042
• Description: LCD Module Calibrator
• Manufacturer: Intersil Corporation

Table 1 gives the calculated value of VOUT for resistors
values of: R
V
R
The external R
that determines the lowest voltage of the external voltage
divider R
to be less than 120μA. The minimum R
A
applications with A
24.9kΩ will result in a set current equal to 20μA.
Power Supply Sequence
The recommendation for power supply sequence would be
to power down the part first (Vdd, AVdd), after 100msec if
programming has occurred, and then power down the
control power supplies (CTL, CE).
Verifying the Programmed Value
The following sequence can be used to verify the
programmed value without having to sequence the V
supply. To verify the programmed value, follow the steps
below. The ISL45042 will read memory contents and be set
to that value when the CE pin is grounded.
1. Power up the ISL45042.
2. CE pin = V
3. Change counter value with CTL pin to desired value.
4. CTL = more than 4.9V and 200msec. Counter value
5. Change the counter value with CTL pin to a different
6. CE pin = Ground.
7. Check that the output value is the one programmed in
ADD
VDD
SET
programmed.
value.
step #4.
SETTING VALUE
TABLE 1. CALCULATED VCOM OUTPUT VOLTAGES
= 10V.
equal to 10V is 4.17kΩ (10V/(20*120μA). Typical
Resistor
1
and R
100
110
128
SET
10
20
30
40
50
60
70
80
90
1
SET
DD.
2
= 24.9kΩ, R1 = 200kΩ, R2 = 243kΩ, and
(Figure 1). The maximum I
VDD
resistor sets the full-scale sink current
equal to 10V and R
6
SET
VOUT
5.468
5.313
5.141
4.969
4.797
4.625
4.453
4.281
4.109
3.936
3.764
3.592
3.282
SET
resistor with
SET
equal to
current has
DD
ISL45042
Generating VDD and CE supply from a Larger
Voltage Source
The CE pin has an internal pull-down resistor (R
Figure 5). The impedance of this resistor is 400kΩ-500kΩ. If
your design is using a resistor divider network to generate
the 3.3V supply (for both V
programming) from a larger voltage source, the 400kΩ
(worst case) resistor needs to be taken into account as a
parallel resistance when the CE pin is connected to this
source. Another design concern is to be able to provide
enough supply current during programming. The ISL45042
draws about 2mA during this process. Recommended
resistor values are shown in Figure 5. This design will result
in an additional 0.83mA quiescent current flowing through
resistors R
ISL45042 Truth Table
The ISL45042 truth table is shown in Table 2. For proper
operation the CE should be disabled (pulled low) before
powering the device down to assure that the glitches and
transients will not cause unwanted EEPROM overwriting.
Mid to Lo
Mid to Hi
>4.9V
FIGURE 5. APPLICATION GENERATING VDD AND VCE
CTL
X
VCC= 5V
VCE
INPUT
A
CE
Lo
Hi
Hi
Hi
and R
4kΩ
VOLTAGES
R
2kΩ
R
B
A
CE
TABLE 2. TRUTH TABLE
B
VDD
VDD
VDD
VDD
VDD
..
R
INTERNAL
DD
No Change Increased
No Change Increased
Decrement
Increment
and CE to enable
OUT
ISL45042
= 400kΩ to 500kΩ
OUTPUT
Normal
Normal
ICC
November 14, 2006
CE LOGIC
INTERNAL
MEMORY
Program
Read
FN6072.6
X
X