pca9952 NXP Semiconductors, pca9952 Datasheet - Page 19

• Manufacturer Part Number: pca9952
• Description: 16-channel Fm+ I 2c-bus 57 Ma Constant Current Led Driver
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA9952_PCA9955
Product data sheet
7.3.15.1 Adjusting output peak current
7.3.14 IREFALL register: output current value for all LEDn outputs
7.3.15 LED driver constant current outputs
The output current setting for all outputs is held in this register. When this register is
written to or updated, all LEDn outputs will be set to a current corresponding to this
register value.
Write to IREF0 to IREF15 will overwrite the output current settings.
Table 17.
Legend: * default value.
In LED display applications, PCA9952/55 provides nearly no current variations from
channel to channel and from device to device. The maximum current skew between
channels is less than 6 % and less than 8 % between devices.
The PCA9952/55 scales up the reference current (I
sink the output current (I
outputs can be set using R
the outputs is independently programmable using command registers IREF0 to IREF15.
Alternatively, programming the IREFALL register allows all outputs to be set at one current
value determined by the value in IREFALL register.
Equation 4
current values that can be programmed for the outputs for a chosen R
For a given IREFx setting,
Example 1: If R
So each channel can be programmed with its individual IREFx in 256 steps and in 225 A
increments to a maximum output current of 57.375 mA independently.
Example 2: If R
So each channel can be programmed with its individual IREFx in 256 steps and in
112.5 A increments to a maximum output channel of 28.687 mA independently.
I
I
Bit
7:0
O
O
_LED_LSB
_LED_MAX
Symbol
IREFALL
IREFALL - Output gain control for all LEDn outputs (address 43h) bit description
and
=
All information provided in this document is subject to legal disclaimers.
=
Equation 5
ext
ext
900 mV
------------------ -

255
= 1 k, I
= 2 k, I
R
Access
write only
ext
Rev. 1 — 2 December 2011

O
I

O
16-channel Fm+ I
) at each output port. The maximum output peak current for the
ext
_LED_LSB
I
1
-- -
4
can be used to calculate the minimum and maximum constant
O
O
O
_LED_LSB = 225 A, I
_LED_LSB = 112.5 A, I
. In addition, the constant value for current drive at each of
_LED
Value
00h*
=

IREFx
=


900 mV
------------------ -
2
C-bus 57 mA constant current LED driver
R

Description
Current gain setting for all LEDn outputs.
ext
PCA9952; PCA9955
900 mV
------------------ -
R
ext
ref

O
) set by the external resistor (R
_LED_MAX = 57.375 mA.
255
-------- -
O
4
_LED_MAX = 28.687 mA.



1
-- -
4
.
ext
© NXP B.V. 2011. All rights reserved.
.
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ext
) to
(4)
(5)