PCA9620H NXP [NXP Semiconductors], PCA9620H Datasheet - Page 33

• Manufacturer Part Number: PCA9620H
• Description: Universal LCD driver for low multiplex rates
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA9620
Product data sheet
7.4.5 Charge pump driving capability
7.4.6 Charge pump frequency settings and power efficiency
Figure 25
deliver.
The output resistance of the charge pump is specified in
values it can be calculated how much current the charge pump can drive under certain
conditions.
Example: Assuming the user would like to have the normal operation point at 25 °C with
V
theoretical value of V
the theoretical maximum value and desired one is 3.0 V. The charge pump resistance is
nominally 0.85 kΩ.
deliver:
For this example we get:
In cases where no extreme driving capability is needed, a command is available for
decreasing the charge pump frequency (see
total current consumption. If the charge pump frequency is halved, then the driving
capability is halved as well, whereas the output resistance doubles.
The PCA9620 offers the possibility to use different frequency settings for the charge
pump. Bit CPF controls the frequency at which the charge pump is running (see
on page
but also on the charge pump driving capability. Using a lower charge pump frequency
decreases the current consumption and the driving capability.
The power efficiency of the charge pump determines in certain applications which
frequency settings to choose for the CPF bit. In the example shown in
current consumption was measured with the charge pump set to 2 × V
V
setup, which is close to 6.0 V. The current load on pin V
delivered by the IC:
The current consumption on pin V
I
P
load
Fig 25. Charge pump model (used to characterize the driving strength)
LCD
DD2
o
=
= 7.0 V and V
= 3.0 V and VPR[7:0] set to maximum to obtain the maximum possible V
=
I
load
ΔV
11). This frequency has a direct influence on the current consumption of the IC
illustrates the main factor determining how much current the charge pump can
×
LCD
V
LCD
⁄
All information provided in this document is subject to legal disclaimers.
R
Theoretical V
V
V
o cp
LCD
LCD
(
DD2
Equation 7
= 2 × V
= 3 × V
)
LCD
Rev. 1 — 9 December 2010
= 5.0 V and the charge pump is set to 2 × V
is 10.0 V and the desired one is 7.0 V. The difference between
I
DD2
DD2
LCD
load
or
value
shows the possible current that the charge pump could
=
3.0 V 0.85 kΩ
DD2
determines the input power taken by the IC:
⁄
Output Resistance
R
o(cp)
Universal LCD driver for low multiplex rates
Table 22 on page
=
Regulated desired V
This supplies the segments
and backplanes
3.5 mA
LCD
Table 35 on page
determines the output power
11) and thus reducing the
LCD
013aaa259
DD2
PCA9620
DD2
. Then the
Figure
© NXP B.V. 2010. All rights reserved.
and with
55. With these
LCD
26, the
Table 22
with this
33 of 71
(7)
(8)