ncp5890 ON Semiconductor, ncp5890 Datasheet - Page 9

• Manufacturer Part Number: ncp5890
• Description: Light Management Ic Dedicated For Lcd Backlighting And Multi-led Fun Light Applications
• Manufacturer: ON Semiconductor

ILED Peak Current
current (I
register. The I2C port is used to setup the ILED peak current
stored into the ILEDREG register. The load current is
derived from the 1144 mV reference voltage provided by
the internal Band Gap associated to the external resistor
connected across I
maximum ILED current is given by the internal current
mirror ratio (multiplier − k−) equal to 250. In other words,
NOTE:
Table 3. Registers Identification
DEC
The ILED peak current depends upon the reference
10
12
13
14
15
16
11
1
2
3
4
5
6
7
8
9
The I
REF
Shut Down the chip
Select I−LED current setup and immediate LED update
Select I−LED target Gradual Dimming command UP
Select I−LED target Gradual Dimming command DOWN
Set Timing & Start gradual Dimming Sequence
Select PWM0 register
Select PWM1 register
Select PWM2 register
Set up Photo sense input stage gain
Set up Photo Sense I−LED minimum value
Set up Photo Sense timing
RFU
RFU
RFU
RFU
Reserved for manufacturing test: do not access
GND
REF
pin ) and the digital contents of the ILEDREG
pin must never be biased by an external voltage higher than 1144 mV.
REF
R2
12k
pin and Ground (see Figure 8). The
1
Register functions
Figure 8. Basic Reference Current Source
U2
http://onsemi.com
+Vbat
1144 mV
9
to get a 25 mA maximum, with a full $1F command, the
reference current should be 25 mA/250 = 100 mA. This
current is used to calculate the resistor connected between
the IREF pin and GND: R
In any case, no voltage shall be forced at I
downward or upward.
better, with a 100 ppm thermal coefficient, to get the
expected overall tolerance.
The tolerance of the external resistor must be 1% or
GND
Register Identification
ILEDREG[4..0]
PHGAIN[4..0]
PHCLK[5..0]
PHMIN[3..0]
FTEST[7..0]
PWM0[4..0]
PWM1[4..0]
PWM2[4..0]
GDIM[4..0]
GDIM[4..0]
TDIM[4..0]
REF
I2C
SDN
= 1.144 / 100e−6 = 11.44 kW.
Control
Digital
ILED
REF
Command
ILED
pin, either
$0A
$0B
$0C
$0D
$0E
$0F
$00
$01
$02
$03
$04
$05
$06
$07
$08
$09