ANALOG DEVICES UG-005 Service Manual

Software User Guide

V

UG-005

One Technology Way • P. O . Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel : [phone] • Fax : [phone] • www.analog.com

ADP8860 Software User Guide

INTRODUCTION

This user guide describes the functionality of the Analog
Devices, Inc., ADP8860 and provides software development
guidelines. The ADP8860 communicates with an external
processor using an I

2

C interface and an interrupt line (nINT).
The processor sends initialization and activation commands
to the ADP8860, which acts as a slave device.

The interrupt line, from the ADP8860 to the processor, is used
to indicate a failure condition, such as a thermal shutdown or
an overvoltage and LED/output short circuit, or to indicate a

V

OUT

light level threshold has been crossed. All interrupt sources are
maskable. Refer to Figure 1 for a typical application diagram.
Figure 2 shows a schematic with keypad light control.

The interrupt line is active low; each interrupt source has an
individual masking bit. The processor can reset the ADP8860
anytime by pulling the nRST line low; this operation reinitia­lizes the ADP8860 at the default state and places the device
in standby mode.

OPTIONAL

PHOTOSENSOR

ALS

PHOTOSENSOR

0.1µF

0.1µF

V

A2

A1

C1

B1

B2

C1+

C1–

C2+

C2–

1µF

OUT

C1
1µF

C2
1µF

08158-001

V

nRST

SDA

SCL

nINT

IN

1µF

VDDIO

VDDIO

VDDIO

VDDIO

D3D1E3D2E4D3D4D4C4D5B4

A3

E1

ADP8860

C2

E2

D2

A4

GND1

D6/

CMP_IN2

D1

GND2

D7C3CMP_IN

B3

Figure 1. Typical Application Schematic with Optional Second Photo Diode

Rev. 0 | Page 1 of 44

UG-005 Software User Guide

TABLE OF CONTENTS

ADP8860 Software User Guide ...................................................... 1

Introduction ...................................................................................... 1

Revision History ............................................................................... 2

I2C Interface Mode ........................................................................... 4

Interrupts ........................................................................................... 5

Data Flow Diagrams ......................................................................... 6

Setting the LED Current .................................................................. 8

Fade Override Mode .................................................................. 14

Setting Backlight and Sink Timings ............................................. 15

Controlling Backlight Settings .................................................. 15

REVISION HISTORY

7/09—Revision 0: Initial Version

Controlling Sink Settings .......................................................... 15

Light Sensing Comparator ............................................................ 17

Conventions .................................................................................... 19

Functional Flowcharts ................................................................... 20

Registers Map .................................................................................. 30

Pseudocode Implementation ........................................................ 31

Listing for ADP8860_Regs.h .................................................... 31

Listing for ADP8860 Constants.h ............................................ 36

Listing for ADP8860 Reset.h .................................................... 38

Listing for ADP8860 MainProgram.c...................................... 39

Rev. 0 | Page 2 of 44

Software User Guide UG-005

KEYPAD LIGHT

UP TO 10 LEDs (6mA EACH)

60mA MAX TOTAL CURRENT

VDDIO

I

CONTRO L

SIGNALS

V

IN

R1 R2 R3 R4

nRST

2

C

nINT

1µF

DISPLAY BACKLI GHT

DL1

DL2

DL3

D3

E3

D1

VIN

A3

GND1

A4

D1

GND2

nRST

E1

SDA

C2

SCL

E2

nINT

D2

E4

D2

D3

Figure 2. Schematic with Keypad Light Control

DL4

D4

D4

ACCESSORY

LIGHTS OR

SUB-DISPLAY BL

DL5

DL6

C4

B4

D5

D6/

CMP_IN2

ADP8860

DL7R5DL8

R6

B3

D7C3CMP_IN

VOUT

C1+

C1–

C2+

C2–

DL17

R15

2.8V

PH2

OPTIONAL

PHOTOSENSOR

0.1µF

A2

A1

C1

B1

B2

1µF

C1
1µF

C2
1µF

PH1

MAIN

PHOTOSENSOR

0.1µF

08158-002

Rev. 0 | Page 3 of 44

UG-005 Software User Guide

I2C INTERFACE MODE

The ADP8860 includes an I2C-compatible serial interface for
controlling the LED current, as well as for readback of system
status registers. The I

2

C device address is 0x54 (0101 0100,
binary) for a write sequence and 0x55 (0101 0101, binary) for
a read sequence. Figure 3 shows the I

2

C write sequence while

Figure 4 shows a read operation.

B7 B0 B7 B0 B7 B0

ST ACK REGISTER ADDRESS ACK REGISTER VALUE

0101010

R/W

The ADP8860 sends data from the register denoted by the
register address. The lowest bit number (0) represents the least
significant bit, and the highest bit number (7) represents the
most significant bit. The register address content selects which
of the ADP8860 registers data is written to or read from.

ACK

ST

START

SLAVE TO MASTER

MASTER TO SLAVE

DEVICE ID

0x54 FOR WRI TE

OPERATIO N

SELECT ADP8860 REGISTER TO

WRITE I N THE 0x00 TO 0x24 AND

WRITE = 0

FROM ADP8860

0x2E RANGE

Figure 3. I

2

C Write Operation

8-BIT VALUE TO WRITE IN THE

ADDRESSED REGIST ER

FROM ADP8860

FROM ADP8860

STOP

08158-003

B7 B0 B7 B0 B7 B0

ST

DEVICE ID

0x54 FOR WRI TE

START

OPERATION

SLAVE TO MASTER

MASTER TO SLAVE

R/W

ACK REGISTER ADDRESS ACK ACK REGISTER VALUE ACK0101010

SELECT ADP8860 REGISTER TO

WRITE I N THE 0x00 TO 0x24 AND

WRITE = 0

FROM ADP8860

0x2E RANGE

Figure 4. I

B7 B0

RS0101010

DEVICE ID

0x55 FOR READ

OPERATION

FROM ADP8860

REPEATED START

2

C Read Operation

R/W

8-BIT VALUE TO WRITE IN THE

READ = 1

ADDRESSED REGIST ER

FROM MASTER

ST

STOP

08158-004

Rev. 0 | Page 4 of 44

Software User Guide UG-005

INTERRUPTS

There are up to five interrupt sources available on the ADP8860
as follows:

• CMP_INT is from the main light sensor comparator.

• CMP2_INT is from sensor Comparator 2.

• OVP_INT is from the overvoltage protection comparator.

• TSD_INT is from the thermal shutdown circuit.

• SHORT_INT is from the short-circuit detection

comparator.
Each interrupt has individual masking/enable bits mapped in
Register INTR_EN. If the respective bit in the masking register
is 0, an interrupt is not generated to the external processor,
however the interrupt pending bit (on the MDCR2 register) can
be set in case the monitored condition occurs. This can be used
by the processor to periodically poll the interrupt pending
register (Register MDCR2) looking for an event to be true. If
the masking register bit is 1 an interrupt is generated (the nINT
line goes low) to the external processor in case an interrupt
pending bit is set.

CMP_INT is set every time the main light sensor comparator
detects a threshold transition (rising or falling condition). This
comparator has two programmable thresholds (L2 and L3)
defining the transition level from dark to office (L3) and from
office to outdoor (L2).

The CMP2_INT interrupt works the same way as CMP_INT
except that the sensing input comes from the second light
sensor. The programmable threshold is the same as the main
light sensor comparator.

The OVP_INT interrupt is generated when the charge pump
output voltage rises above a safety limit. In the event of an over-

voltage condition, the charge-pump is disabled until the output
voltage decreases to a recovery working level. An overvoltage
event can be generated when the load is removed from the
circuit and the input voltage, multiplied by the charge pump
gain (can be 1.5× or 2×), is above the OVP limit. In this con­dition, the interrupt to the external processor is generated
periodically. Therefore, the software should handle a case of
this sort by turning off the ADP8860 or disabling the OVP
interrupt mask.

The TSD_INT interrupt is generated when the die temperature in
the ADP8860 rises above a safety limit, typically 150°. When this
condition occurs, the charge pump and the LED drivers are turned
off waiting for the die to cool down. When the die temperature
decreases below ~130° the circuit is activated again automatically.
No interrupt is generated when the device turns on again, however
if the software clears the pending interrupt and the temperature
remains above 130° another interrupt is generated.

The SHORT_INT interrupt is generated if the output of the
charge-pump VOUT is shorted to ground or an LED connected
to the sink output is shorted. In a short-circuit event, the charge
pump and drivers are turned off immediately and the short­circuit pending flag is set. The processor may then retry new
activations or issue a diagnostic message. Interrupts are cleared
by writing a 1 in the pending register bit. If Bit INT_CFG in
Register MDCR is set to 1, this forces the nINT line deassertion
(Logic High) for 50 μs after the processor clears the interrupt
pending, and the interrupt condition persists. If INT_CFG is 0,
the nINT line remains asserted (Logic Low) after the processor
clears the interrupt pending and the interrupt condition
persists.

MDCR (0x01)

BIT 6

INT_CFG

50µs

INT

INTERRUPT

DE-ASSERTI ON

INT_CLEAR

(ASSERTED WHEN WRITING

THE INTERRUPT PENDING

FLAGS I N MDCR2)

BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

SHORT_IEN CMP_IENCMP2_IENOVP_IENTSD_IEN

SHORT_INT TSD_INT OVP_INT CMP2_INT CMP_INT

BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

Figure 5. Interrupt Logic

Rev. 0 | Page 5 of 44

INTR_EN (0x03) – INTERRUPT MASKS

MCDR2 (0x02) – INT ERRUPT PENDING

08158-005

UG-005 Software User Guide

DATA FLOW DIAGRAMS

Figure 6 and Figure 7 show the backlight data flow and the individual data flow, respectively.

NSTBY = 0

OR VIN < UVLO

TURN OFF
BACKLIGHT
AND ISINKS

STANDBY

BLEN = 0

OR TSD_INT = 1

OR SHORT_INT = 1

NSTBY = 1

NO COMMAND

BLEN AND

FOVR = 1

FADE IN

TO DIM

BLEN = 1

BL_FO TIMEOUT

WAITING

COMMAND

DIM_EN AND

BLEN = 1

BACKLIGHT

DIM STATE

(OFFT)

BACKLIGHT

FADE IN
TO MAX

BL_FI TIMEOUT

DIMT = DISABL ED

BACKLIGHT

ACTIVATIO N

TIME (DIMT)

DIM_EN = 1

AND DIMT TIM EOUT

BACKLIGHT

NOTES

1. DASHED LINE INDICATES AN INTERRUPT O R AN EVENT THAT CAN HAPPEN ANYTI ME DURING THE DEVICE O PERATION.

2. COMMANDS FRO M I
COMMANDS TO MAKE THE FLOW REPRES ENTATION CLEARER.

2

C ARE ALWAYS MO NITORED AND EXECUTED. T HE FLOW SHOWS A COMMON BUBBLE FOR

NSTBY = 0

DIM_EN = 0

AND DIMT = DISABL ED

OFFT TIMEOUT

AND DIM_EN = 0

DIM_EN = 1 OR
OFFT = DISABLED

BACKLIGHT

OFF

BL_FO TIMEOUT

BACKLIGHT

FADE OUT

Figure 6. Backlight Data Flow

TO OFF

08158-006

Rev. 0 | Page 6 of 44

Software User Guide UG-005

OR TIMEOUT

SCx OFF = 0

(ALWAYS ON)

ACTIVATIO N

INDIVIDUAL

xSINK

TIMEOUT

SCFI = 0

SCON

NSTBY = 0

OR VIN < UVLO

BACKLIGHT
AND ISINKS

xSINK

FADE-IN

FADE-OUT

TURN OFF

STANDBY

NSTBY = 1

NO COMMAND

WAITING

SCx_EN = 1

SCx OFF

TIMEOUT

SCx_EN = 0 SCx_EN = 0

xSINK

COMMAND

TURN OFF

INDIVIDUAL

SCFO = 0

OR TIMEOUT

SINK

NSTBY = 0

SIS_EN = 1

AND ISCC = 0

ENABLED

SINKS

FADE-IN

OR TIMEOUT

xSINK

SCFO = 0

OR TIMEOUT

SCFI = 0

SCx_EN = 0

OR TSD_INT = 1

OR SHORT_INT = 1

OFF

ENABLED

SINKS

FADE-OUT

ACTIVATE
ENABLED

SIS_EN = 0

OR ISCC ≠ 0

SINKS

SIS_EN = 1

AND ISCC = 0

NOTES

1. DASHED LINE INDICATES AN INTERRUPT O R AN EVENT THAT CAN HAPPEN ANYTI ME DURING THE DEVICE OPERATION.

Figure 7. Individual Sinks Data Flow

Rev. 0 | Page 7 of 44

08158-007

UG-005 Software User Guide

SETTING THE LED CURRENT

The ADP8860 contains seven current sink outputs that can be
software configured to operate as part of the LED backlight or
as individual sinks, such as funlights or keypad lights. All
outputs can drive up to 30 mA with the exception of the seventh
sink (D1B/LED7) that can drive up to 60 mA, which is ideal for
keypad light applications where up to 10 LEDs can be driven in
parallel with shunt resistors (see Figure 2).

The application software must program which output to use as
part of the backlight and which to use for the individual sinks.
Register BLSEN is used for this purpose. If the selection bit
associated with the LED sink (Bit 0 controls LED1, Bit 1
controls LED2, and so on) is set to 0, it is part of the LED
backlight; otherwise, if set to 1, it is an independent sink. In
this case, Register ISCC controls the individual sink turn-on
and turn-off activations. For example, if BLSEN is programmed
with 0x70, LED1 to LED4 are used for the backlight while LED5
to LED7 are individual sinks. Bit 7 in BLSEN is not used.

In backlight operation, there are three distinct selectable bright­ness levels: dark, office, and daylight. Each brightness level has
two programmable settings:

• The MAX brightness defined in Register BLMX1 (day-

light), Register BLMX2 (office), and Register BLMX3
(dark) can range from 0 mA to 30 mA.

• The DIM brightness level defined in Register BLDM1 for

daylight, Register BLDM2 for office, and Register BLDM3
for dark can range from 0 mA to 30 mA.

The backlight LED current depends on the backlight transfer
law, linear or square, programmed in the CFGR register Bit 2
and Bit 1. Tabl e 2 shows all the current values available
according to the control law selected.

The transfer function for the linear law is

__

ISCALEFULL

⎞
⎟
⎠

RegValue

⎛

_

RegValueIBACKLIGHT (1)

= (2)

×=

⎜
⎝

IBACKLIGHT

127_ ×

ISCALEFULL

__

127

where:

BACKLIGHT_I is the desired LED current in mA.
RegValue is the digital 7-bit value programmed in the backlight

current registers.

FULL_SCALE_I is the maximum backlight current value, which

is 30 mA.

The transfer function for the square law is

2

⎞

__Re

ISCALEFULLgValue

(3)

⎟
⎟
⎠

RegValue

⎛
⎜

_

=

IBACKLIGHT

⎜
⎝

=

×

127

IBACKLIGHT

_127 ×

(4)

ISCALEFULL

__

Table 1. Backlight Transfer Laws—CFGR Register Bits[2:1]

Bits[2:1] Fading Law Fading Time Change

00 Linear Law DAC Linear time steps
01 Square Law DAC Linear time steps
10

11

Square Law DAC
(Cubic 1)

Square Law DAC
(Cubic 2)

Nonlinear time steps
(Type 1)

Nonlinear time steps
(Type 2)

The complete set of square law current values are given in
Tabl e 2.

Rev. 0 | Page 8 of 44

Software User Guide UG-005

Table 2. Linear and Square Law Current Values

DAC Code Linear Law (mA) Square Law (mA)

0x00 0 0.000
0x01 0.236 0.002
0x02 0.472 0.007
0x03 0.709 0.017
0x04 0.945 0.030
0x05 1.181 0.047
0x06 1.417 0.067
0x07 1.654 0.091
0x08 1.890 0.119
0x09 2.126 0.151
0x0A 2.362 0.186
0x0B 2.598 0.225
0x0C 2.835 0.268
0x0D 3.071 0.314
0x0E 3.307 0.365
0x0F 3.543 0.419
0x10 3.780 0.476
0x11 4.016 0.538
0x12 4.252 0.603
0x13 4.488 0.671
0x14 4.724 0.744
0x15 4.961 0.820
0x16 5.197 0.900
0x17 5.433 0.984
0x18 5.669 1.071
0x19 5.906 1.163
0x1A 6.142 1.257
0x1B 6.378 1.356
0x1C 6.614 1.458
0x1D 6.850 1.564
0x1E 7.087 1.674
0x1F 7.323 1.787
0x20 7.559 1.905
0x21 7.795 2.026
0x22 8.031 2.150
0x23 8.268 2.279
0x24 8.504 2.411
0x25 8.740 2.546
0x26 8.976 2.686
0x27 9.213 2.829
0x28 9.449 2.976
0x29 9.685 3.127
0x2A 9.921 3.281
0x2B 10.157 3.439
0x2C 10.394 3.601
0x2D 10.630 3.767
0x2E 10.866 3.936
0x2F 11.102 4.109

DAC Code Linear Law (mA) Square Law (mA)

0x30 11.339 4.285
0x31 11.575 4.466
0x32 11.811 4.650
0x33 12.047 4.838
0x34 12.283 5.029
0x35 12.520 5.225
0x36 12.756 5.424
0x37 12.992 5.627
0x38 13.228 5.833
0x39 13.465 6.043
0x3A 13.701 6.257
0x3B 13.937 6.475
0x3C 14.173 6.696
0x3D 14.409 6.921
0x3E 14.646 7.150
0x3F 14.882 7.382
0x40 15.118 7.619
0x41 15.354 7.859
0x42 15.591 8.102
0x43 15.827 8.350
0x44 16.063 8.601
0x45 16.299 8.855
0x46 16.535 9.114
0x47 16.772 9.376
0x48 17.008 9.642
0x49 17.244 9.912
0x4A 17.480 10.185
0x4B 17.717 10.463
0x4C 17.953 10.743
0x4D 18.189 11.028
0x4E 18.425 11.316
0x4F 18.661 11.608
0x50 18.898 11.904
0x51 19.134 12.203
0x52 19.370 12.507
0x53 19.606 12.814
0x54 19.842 13.124
0x55 20.079 13.439
0x56 20.315 13.757
0x57 20.551 14.078
0x58 20.787 14.404
0x59 21.024 14.733
0x5A 21.260 15.066
0x5B 21.496 15.403
0x5C 21.732 15.743
0x5D 21.968 16.087
0x5E 22.205 16.435
0x5F 22.441 16.787

Rev. 0 | Page 9 of 44

UG-005 Software User Guide

DAC Code Linear Law (mA) Square Law (mA)

0x60 22.677 17.142
0x61 22.913 17.501
0x62 23.150 17.863
0x63 23.386 18.230
0x64 23.622 18.600
0x65 23.858 18.974
0x66 24.094 19.351
0x67 24.331 19.733
0x68 24.567 20.118
0x69 24.803 20.507
0x6A 25.039 20.899
0x6B 25.276 21.295
0x6C 25.512 21.695
0x6D 25.748 22.099
0x6E 25.984 22.506
0x6F 26.220 22.917

DAC Code Linear Law (mA) Square Law (mA)

0x70 26.457 23.332
0x71 26.693 23.750
0x72 26.929 24.173
0x73 27.165 24.599
0x74 27.402 25.028
0x75 27.638 25.462
0x76 27.874 25.899
0x77 28.110 26.340
0x78 28.346 26.784
0x79 28.583 27.232
0x7A 28.819 27.684
0x7B 29.055 28.140
0x7C 29.291 28.599
0x7D 29.528 29.063
0x7E 29.764 29.529
0x7F 30.000 30.000

Rev. 0 | Page 10 of 44

Software User Guide UG-005

If the automatic light sensing control is enabled (CMP_AUTOEN,
Bit 1, is set to 1 in Register MDCR) the result from the light
sensing comparator controls the backlight brightness in one of
the three levels (dark, office, and daylight).

In this mode, it is not possible to force, by software, a defined
level. Thus, settings on Bits[4:3] (BLV) in the CFGR register are
not considered in automatic light sensing mode. In case the
automatic light sensing mode is disabled (0 is written to
CMP_AUTOEN in the MDCR register), software can force the
backlight brightness in one of the three possible modes (dark,
office, or daylight) by writing Bits[4:3] (BLV) in Register CFGR
(see Tabl e 3).

Table 3. Brightness Level—Bits[4:3] (BLV) in CFGR Register

Bits[4:3] Backlight Brightness Level

00 Level 1 (daylight)
01 Level 2 (office)
10 Level 3 (dark)
11 Disabled

Each individual sink has a dedicated current register defining
its brightness level. As with the backlight, the current level
depends on the transfer law selected in the ISCFR register
Bits[1:0] (SC_LAW).

The ISC1 register defines the current level for LED1, the ISC2
register defines the level for LED2, and so on until ISC7, which
controls the current for LED7. The maximum current level
programmable is 30 mA. However, LED7 can be set up to
60 mA if Bit 7 in the ISC7 register is set to 1. The possible
current levels for 30 mA are listed in Tab le 2 .

Rev. 0 | Page 11 of 44

UG-005 Software User Guide

Table 4. Complete Set of Square Law Current Values for LED7
—60 mA Range

DAC Code Linear Law (mA) Square Law (mA)

0x00 0.000 0
0x01 0.472 0.004
0x02 0.945 0.014
0x03 1.42 0.034
0x04 1.89 0.06
0x05 2.36 0.094
0x06 2.83 0.134
0x07 3.31 0.182
0x08 3.78 0.238
0x09 4.25 0.302
0x0A 4.72 0.372
0x0B 5.20 0.45
0x0C 5.67 0.536
0x0D 6.14 0.628
0x0E 6.61 0.73
0x0F 7.09 0.838
0x10 7.56 0.952
0x11 8.03 1.076
0x12 8.50 1.206
0x13 8.98 1.342
0x14 9.45 1.488
0x15 9.92 1.64
0x16 10.39 1.8
0x17 10.87 1.968
0x18 11.34 2.142
0x19 11.81 2.326
0x1A 12.28 2.514
0x1B 12.76 2.712
0x1C 13.23 2.916
0x1D 13.70 3.128
0x1E 14.17 3.348
0x1F 14.65 3.574
0x20 15.12 3.81
0x21 15.59 4.052
0x22 16.06 4.3
0x23 16.54 4.558
0x24 17.01 4.822
0x25 17.48 5.092
0x26 17.95 5.372
0x27 18.43 5.658
0x28 18.90 5.952
0x29 19.37 6.254
0x2A 19.84 6.562
0x2B 20.31 6.878
0x2C 20.79 7.202
0x2D 21.26 7.534

DAC Code Linear Law (mA) Square Law (mA)

0x2E 21.73 7.872
0x2F 22.20 8.218
0x30 22.68 8.57
0x31 23.15 8.932
0x32 23.62 9.3
0x33 24.09 9.676
0x34 24.57 10.058
0x35 25.04 10.45
0x36 25.51 10.848
0x37 25.98 11.254
0x38 26.46 11.666
0x39 26.93 12.086
0x3A 27.40 12.514
0x3B 27.87 12.95
0x3C 28.35 13.392
0x3D 28.82 13.842
0x3E 29.29 14.3
0x3F 29.76 14.764
0x40 30.24 15.238
0x41 30.71 15.718
0x42 31.18 16.204
0x43 31.65 16.7
0x44 32.13 17.202
0x45 32.60 17.71
0x46 33.07 18.228
0x47 33.54 18.752
0x48 34.02 19.284
0x49 34.49 19.824
0x4A 34.96 20.37
0x4B 35.43 20.926
0x4C 35.91 21.486
0x4D 36.38 22.056
0x4E 36.85 22.632
0x4F 37.32 23.216
0x50 37.80 23.808
0x51 38.27 24.406
0x52 38.74 25.014
0x53 39.21 25.628
0x54 39.69 26.248
0x55 40.16 26.878
0x56 40.63 27.514
0x57 41.10 28.156
0x58 41.57 28.808
0x59 42.05 29.466
0x5A 42.52 30.132
0x5B 42.99 30.806

Rev. 0 | Page 12 of 44

Software User Guide UG-005

DAC Code Linear Law (mA) Square Law (mA)

0x5C 43.46 31.486
0x5D 43.94 32.174
0x5E 44.41 32.87
0x5F 44.88 33.574
0x60 45.35 34.284
0x61 45.83 35.002
0x62 46.30 35.726
0x63 46.77 36.46
0x64 47.24 37.2
0x65 47.72 37.948
0x66 48.19 38.702
0x67 48.66 39.466
0x68 49.13 40.236
0x69 49.61 41.014
0x6A 50.08 41.798
0x6B 50.55 42.59
0x6C 51.02 43.39
0x6D 51.50 44.198

DAC Code Linear Law (mA) Square Law (mA)

0x6E 51.97 45.012
0x6F 52.44 45.834
0x70 52.91 46.664
0x71 53.39 47.5
0x72 53.86 48.346
0x73 54.33 49.198
0x74 54.80 50.056
0x75 55.28 50.924
0x76 55.75 51.798
0x77 56.22 52.68
0x78 56.69 53.568
0x79 57.17 54.464
0x7A 57.64 55.368
0x7B 58.11 56.28
0x7C 58.58 57.198
0x7D 59.06 58.126
0x7E 59.53 59.058
0x7F 60 60

Rev. 0 | Page 13 of 44

UG-005 Software User Guide

Square Cubic Law 1 and Square Cubic Law 2 use the same
square transfer law values with faster increment/decrement
times when fading in and out.

FADE OVERRIDE MODE

The fade override mode is enabled when Bit 0 (FOVR) in the
CFGR register is set to 1. In this mode, the backlight skips the
fade-in time when Bit BLEN in the MDCR register is set to 1
and it goes directly to the programmed maximum backlight

35

30

25

20

15

LED CURRENT (mA)

10

5

0

0 20 40 60 80 100 120

Figure 8. LED Current Transfer Law Curves

LINEAR LAW

SQUARE LAW

DIGITAL VALUE (DAC)

brightness intensity. There remains a 100 ms ramp-up time to
avoid rapid change in current. The fade-in time is not skipped
at the very first activation, after an off condition.

This mode is useful is situations where the backlight is fading
out and the user depresses a keypad button. The system
software can intercept this condition, set the FOVR bit, then
write the BLEN bit to 1 again. Fade-out time is not affected by
the FOVR bit.

08158-008

Rev. 0 | Page 14 of 44