Data Sheet

PCA9955B
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED
driver
Rev. 2 — 20 November 2015
Product data sheet
1. General description
The PCA9955B is an I2C-bus controlled 16-channel constant current LED driver optimized
for dimming and blinking 57 mA Red/Green/Blue/Amber (RGBA) LEDs in amusement
products. Each LED output has its own 8-bit resolution (256 steps) fixed frequency
individual PWM controller that operates at 31.25 kHz with a duty cycle that is adjustable
from 0 % to 100 % to allow the LED to be set to a specific brightness value. An additional
8-bit resolution (256 steps) group PWM controller has both a fixed frequency of 122 Hz
and an adjustable frequency between 15 Hz to every 16.8 seconds with a duty cycle that
is adjustable from 0 % to 99.6 % that is used to either dim or blink all LEDs with the same
value.
Each LED output can be off, on (no PWM control), set at its individual PWM controller
value or at both individual and group PWM controller values. The PCA9955B operates
with a supply voltage range of 3 V to 5.5 V and the constant current sink LED outputs
allow up to 20 V for the LED supply. The output peak current is adjustable with an 8-bit
linear DAC from 225 A to 57 mA.
Gradation control for all current sources is achieved via the I2C-bus serial interface and
allows user to ramp current automatically without MCU intervention. 8-bit DACs are
available to adjust brightness levels for each LED current source. There are four
selectable gradation control groups and each group has independently four registers to
control ramp-up and ramp-down rate, step time, hold ON/OFF time and final hold ON
output current. Two gradation operation modes are available for each group, one is single
shot mode (output pattern once) and the other is continuous mode (output pattern repeat).
Each channel can be set to either gradation mode or normal mode and assigned to any
one of these four gradation control groups.
This device has built-in open, short load and overtemperature detection circuitry. The error
information from the corresponding register can be read via the I2C-bus. Additionally, a
thermal shutdown feature protects the device when internal junction temperature exceeds
the limit allowed for the process.
The PCA9955B device has a Fast-mode Plus (Fm+) I2C-bus interface. Fm+ devices offer
higher frequency (up to 1 MHz) or more densely populated bus operation (up to 4000 pF).
The active LOW output enable input pin (OE) blinks all the LED outputs and can be used
to externally PWM the outputs, which is useful when multiple devices need to be dimmed
or blinked together without using software control.
Software programmable LED Group and three Sub Call I2C-bus addresses allow all or
defined groups of PCA9955B devices to respond to a common I2C-bus address, allowing
for example, all red LEDs to be turned on or off at the same time or marquee chasing
effect, thus minimizing I2C-bus commands. On power-up, PCA9955B has a unique
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Sub Call address to identify it as a 16-channel LED driver. This unique address allows
mixing of devices with different channel widths. Three hardware address pins on
PCA9955B allow up to 125 devices on the same bus.
The Software Reset (SWRST) function allows the master to perform a reset of the
PCA9955B through the I2C-bus, identical to the Power-On Reset (POR) that initializes the
registers to their default state causing the output current switches to be OFF (LED off).
This allows an easy and quick way to reconfigure all device registers to the same
condition.
2. Features and benefits
 16 LED drivers. Each output programmable at:
 Off
 On
 Programmable LED brightness
 Programmable group dimming/blinking mixed with individual LED brightness
 Programmable LED output delay to reduce EMI and surge currents
 Gradation control for all channels
 Each channel can assign to one of four gradation control groups
 Programmable gradation time and rate for ramp-up and/or ramp-down operations
 Programmable step time (6-bit) from 0.5 ms (minimum) to 512 ms (maximum)
 Programmable hold-on time after ramp-up and hold-off time after ramp-down (3-bit)
from 0 s to 6 s
 Programmable final ramp-up and hold-on current
 Programmable brightness current output adjustment, either linear or exponential
curve
 16 constant current output channels can sink up to 57 mA, tolerate up to 20 V when
OFF
 Output current adjusted through an external resistor (REXT input)
 Output current accuracy
 4 % between output channels
 6 % between PCA9955B devices
 Open/short load/overtemperature detection mode to detect individual LED errors
 1 MHz Fast-mode Plus compatible I2C-bus interface with 30 mA high drive capability
on SDA output for driving high capacitive buses
 256-step (8-bit) linear programmable brightness per LED output varying from fully off
(default) to maximum brightness fully ON using a 31.25 kHz PWM signal
 256-step group brightness control allows general dimming (using a 122 Hz PWM
signal) from fully off to maximum brightness (default)
 256-step group blinking with frequency programmable from 15 Hz to 16.8 s and duty
cycle from 0 % to 99.6 %
 Output state change programmable on the Acknowledge or the STOP condition to
update outputs byte-by-byte or all at the same time (default to ‘Change on STOP’).
 Active LOW Output Enable (OE) input pin allows for hardware blinking and dimming of
the LEDs
PCA9955B
Product data sheet
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Rev. 2 — 20 November 2015
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
 Three quinary hardware address pins allow 125 PCA9955B devices to be connected
to the same I2C-bus and to be individually programmed
 4 software programmable I2C-bus addresses (one LED Group Call address and three
LED Sub Call addresses) allow groups of devices to be addressed at the same time in
any combination (for example, one register used for ‘All Call’ so that all the
PCA9955Bs on the I2C-bus can be addressed at the same time and the second
register used for three different addresses so that 1⁄3 of all devices on the bus can be
addressed at the same time in a group). Software enable and disable for each
programmable I2C-bus address.
 Unique power-up default Sub Call address allows mixing of devices with different
channel widths
 Software Reset feature (SWRST Call) allows the device to be reset through the
I2C-bus
 8 MHz internal oscillator requires no external components
 Internal power-on reset
 Noise filter on SDA/SCL inputs
 No glitch on LEDn outputs on power-up
 Low standby current
 Operating power supply voltage (VDD) range of 3 V to 5.5 V
 5.5 V tolerant inputs on non-LED pins
 40 C to +85 C operation
 ESD protection exceeds 4000 V HBM per JESD22-A114
 Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA
 Packages offered: HTSSOP28
3. Applications








PCA9955B
Product data sheet
Amusement products
RGB or RGBA LED drivers
LED status information
LED displays
LCD backlights
Keypad backlights for cellular phones or handheld devices
Fade-in and fade-out for breathlight control
Automotive lighting (PCA9955BTW/Q900)
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Rev. 2 — 20 November 2015
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
4. Ordering information
Table 1.
Ordering information
Type number
Topside mark
Package
Name
Description
Version
PCA9955BTW
PCA9955BTW
HTSSOP28 plastic thermal enhanced thin shrink small outline
package; 28 leads; body width 4.4 mm;
lead pitch 0.65 mm; exposed die pad
SOT1172-3
PCA9955BTW/Q900[1]
PCA9955BTW
HTSSOP28 plastic thermal enhanced thin shrink small outline
package; 28 leads; body width 4.4 mm;
lead pitch 0.65 mm; exposed die pad
SOT1172-3
[1]
PCA9955BTW/Q900 is AEC-Q100 compliant.
4.1 Ordering options
Table 2.
Ordering options
Type number
Orderable
part number
Package
Packing method
Minimum
order
quantity
Temperature
PCA9955BTW
PCA9955BTWJ
HTSSOP28
Reel 13” Q1/T1
*Standard mark SMD
2500
Tamb = 40 C to +85 C
PCA9955BTW/Q900 PCA9955BTW/Q900J HTSSOP28
Reel 13” Q1/T1
*Standard mark SMD
2500
Tamb = 40 C to +85 C
PCA9955B
Product data sheet
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Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
5. Block diagram
AD0 AD1 AD2
REXT
LED0
LED1
LED14
LED15
I/O
REGULATOR
PCA9955B
DAC0
SCL
INPUT FILTER
DAC1
SDA
individual LED
current setting
8-bit DACs
I2C-BUS
CONTROL
DAC
14
DAC
15
POWER-ON
RESET
VDD
OUTPUT DRIVER, DELAY CONTROL,
ERROR DETECTION AND THERMAL SHUTDOWN
VSS
INPUT
FILTER
RESET
LED STATE
SELECT
REGISTER
PWM
REGISTER X
BRIGHTNESS
CONTROL
÷ 256
31.25 kHz
8 MHz
OSCILLATOR
GRADATION
CONTROL
GRPFREQ
REGISTER
DIM CLOCK
MUX/
CONTROL
GRPPWM
REGISTER
'0' – permanently OFF
'1' – permanently ON
OE
aaa-016962
Dim repetition rate = 122 Hz
Blink repetition rate = 15 Hz to every 16.8 seconds
Fig 1.
Block diagram of PCA9955B
PCA9955B
Product data sheet
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PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
6. Pinning information
6.1 Pinning
REXT
1
28 VDD
AD0
2
27 SDA
26 SCL
PCA9955BTW
AD2 4 PCA9955BTW/Q900 25 RESET
AD1
3
OE
5
24 VSS
LED0
6
23 LED15
LED1
7
22 LED14
LED2
8
21 LED13
LED3
9
VSS 10
20 LED12
(1)
19 VSS
LED4 11
18 LED11
LED5 12
17 LED10
LED6 13
16 LED9
LED7 14
15 LED8
aaa-016963
(1) Thermal pad; connected to VSS
Fig 2.
PCA9955B
Product data sheet
Pin configuration for HTSSOP28
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Rev. 2 — 20 November 2015
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
6.2 Pin description
Table 3.
Pin
Type
Description
REXT
1
I
current set resistor input; resistor to ground
AD0
2
I
address input 0
AD1
3
I
address input 1
AD2
4
I
address input 2
OE
5
I
active LOW output enable for LEDs
LED0
6
O
LED driver 0
LED1
7
O
LED driver 1
LED2
8
O
LED driver 2
LED3
9
O
LED driver 3
LED4
11
O
LED driver 4
LED5
12
O
LED driver 5
LED6
13
O
LED driver 6
LED7
14
O
LED driver 7
LED8
15
O
LED driver 8
LED9
16
O
LED driver 9
LED10
17
O
LED driver 10
LED11
18
O
LED driver 11
LED12
20
O
LED driver 12
LED13
21
O
LED driver 13
LED14
22
O
LED driver 14
LED15
23
O
LED driver 15
RESET
25
I
active LOW reset input with external 10 k
pull-up resistor
SCL
26
I
serial clock line
SDA
27
I/O
serial data line
ground
supply ground
power supply
supply voltage
VSS
10, 19, 24
VDD
28
[1]
PCA9955B
Product data sheet
Pin description
Symbol
[1]
HTSSOP28 package supply ground is connected to both VSS pins and exposed center pad. VSS pins must
be connected to supply ground for proper device operation. For enhanced thermal, electrical, and board
level performance, the exposed pad must be soldered to the board using a corresponding thermal pad on
the board and for proper heat conduction through the board, thermal vias must be incorporated in the
printed-circuit board in the thermal pad region.
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7. Functional description
Refer to Figure 1 “Block diagram of PCA9955B”.
7.1 Device addresses
Following a START condition, the bus master must output the address of the slave it is
accessing.
For PCA9955B there are a maximum of 125 possible programmable addresses using the
three quinary hardware address pins.
7.1.1 Regular I2C-bus slave address
The I2C-bus slave address of the PCA9955B is shown in Figure 3. The 7-bit slave
address is determined by the quinary input pads AD0, AD1 and AD2. Each pad can have
one of five states (GND, pull-up, floating, pull-down, and VDD) based on how the input pad
is connected on the board. At power-up or hardware/software reset, the quinary input
pads are sampled and set the slave address of the device internally. To conserve power,
once the slave address is determined, the quinary input pads are turned off and will not be
sampled until the next time the device is power cycled. Table 4 lists the five possible
connections for the quinary input pads along with the external resistor values that must be
used.
Table 4.
Quinary input pad connection
Pad connection
(pins AD2, AD1, AD0)[1]
Mnemonic
Min.
Max.
tie to ground
GND
0
17.9
resistor pull-down to ground
PD
34.8
270
open (floating)
FLT
503

resistor pull-up to VDD
PU
31.7
340
tie to VDD
VDD
0
22.1
[1]
External resistor (k)
These AD[2:0] inputs must be stable before the supply VDD to the chip.
Table 5 lists all 125 possible slave addresses of the device based on all combinations of
the five states connected to three address input pins AD0, AD1 and AD2.
Table 5.
I2C-bus slave address
Hardware selectable input pins I2C-bus slave address for PCA9955B
AD2
AD1
AD0
Decimal Hexadecimal Binary (A[6:0]) Address (R/W = 0)
GND
GND
GND
1
01
0000001[1]
02h
GND
GND
PD
2
02
0000010[1]
04h
03
0000011[1]
06h
04
0000100[1]
08h
0Ah
GND
GND
Product data sheet
GND
FLT
PU
3
4
GND
GND
VDD
5
05
0000101[1]
GND
PD
GND
6
06
0000110[1]
0Ch
07
0000111[1]
0Eh
GND
PCA9955B
GND
PD
PD
7
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Table 5.
I2C-bus slave address …continued
Hardware selectable input pins I2C-bus slave address for PCA9955B
PCA9955B
Product data sheet
AD2
AD1
AD0
Decimal Hexadecimal Binary (A[6:0]) Address (R/W = 0)
GND
PD
FLT
8
08
0001000
10h
GND
PD
PU
9
09
0001001
12h
GND
PD
VDD
10
0A
0001010
14h
GND
FLT
GND
11
0B
0001011
16h
GND
FLT
PD
12
0C
0001100
18h
GND
FLT
FLT
13
0D
0001101
1Ah
GND
FLT
PU
14
0E
0001110
1Ch
GND
FLT
VDD
15
0F
0001111
1Eh
GND
PU
GND
16
10
0010000
20h
GND
PU
PD
17
11
0010001
22h
GND
PU
FLT
18
12
0010010
24h
GND
PU
PU
19
13
0010011
26h
GND
PU
VDD
20
14
0010100
28h
GND
VDD
GND
21
15
0010101
2Ah
GND
VDD
PD
22
16
0010110
2Ch
GND
VDD
FLT
23
17
0010111
2Eh
GND
VDD
PU
24
18
0011000
30h
GND
VDD
VDD
25
19
0011001
32h
PD
GND
GND
26
1A
0011010
34h
PD
GND
PD
27
1B
0011011
36h
PD
GND
FLT
28
1C
0011100
38h
PD
GND
PU
29
1D
0011101
3Ah
PD
GND
VDD
30
1E
0011110
3Ch
PD
PD
GND
31
1F
0011111
3Eh
PD
PD
PD
32
20
0100000
40h
PD
PD
FLT
33
21
0100001
42h
PD
PD
PU
34
22
0100010
44h
PD
PD
VDD
35
23
0100011
46h
PD
FLT
GND
36
24
0100100
48h
PD
FLT
PD
37
25
0100101
4Ah
PD
FLT
FLT
38
26
0100110
4Ch
PD
FLT
PU
39
27
0100111
4Eh
PD
FLT
VDD
40
28
0101000
50h
PD
PU
GND
41
29
0101001
52h
PD
PU
PD
42
2A
0101010
54h
PD
PU
FLT
43
2B
0101011
56h
PD
PU
PU
44
2C
0101100
58h
PD
PU
VDD
45
2D
0101101
5Ah
PD
VDD
GND
46
2E
0101110
5Ch
PD
VDD
PD
47
2F
0101111
5Eh
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Table 5.
I2C-bus slave address …continued
Hardware selectable input pins I2C-bus slave address for PCA9955B
PCA9955B
Product data sheet
AD2
AD1
AD0
Decimal Hexadecimal Binary (A[6:0]) Address (R/W = 0)
PD
VDD
FLT
48
30
0110000
60h
PD
VDD
PU
49
31
0110001
62h
PD
VDD
VDD
50
32
0110010
64h
FLT
GND
GND
51
33
0110011
66h
FLT
GND
PD
52
34
0110100
68h
FLT
GND
FLT
53
35
0110101
6Ah
FLT
GND
PU
54
36
0110110
6Ch
FLT
GND
VDD
55
37
0110111
6Eh
FLT
PD
GND
56
38
0111000
70h
FLT
PD
PD
57
39
0111001
72h
FLT
PD
FLT
58
3A
0111010
74h
FLT
PD
PU
59
3B
0111011
76h
FLT
PD
VDD
60
3C
0111100
78h
FLT
FLT
GND
61
3D
0111101
7Ah
FLT
FLT
PD
62
3E
0111110
7Ch
FLT
FLT
FLT
63
3F
0111111
7Eh
FLT
FLT
PU
64
40
1000000
80h
FLT
FLT
VDD
65
41
1000001
82h
FLT
PU
GND
66
42
1000010
84h
FLT
PU
PD
67
43
1000011
86h
FLT
PU
FLT
68
44
1000100
88h
FLT
PU
PU
69
45
1000101
8Ah
FLT
PU
VDD
70
46
1000110
8Ch
FLT
VDD
GND
71
47
1000111
8Eh
FLT
VDD
PD
72
48
1001000
90h
FLT
VDD
FLT
73
49
1001001
92h
FLT
VDD
PU
74
4A
1001010
94h
FLT
VDD
VDD
75
4B
1001011
96h
PU
GND
GND
76
4C
1001100
98h
PU
GND
PD
77
4D
1001101
9Ah
PU
GND
FLT
78
4E
1001110
9Ch
PU
GND
PU
79
4F
1001111
9Eh
PU
GND
VDD
80
50
1010000
A0h
PU
PD
GND
81
51
1010001
A2h
PU
PD
PD
82
52
1010010
A4h
PU
PD
FLT
83
53
1010011
A6h
PU
PD
PU
84
54
1010100
A8h
PU
PD
VDD
85
55
1010101
AAh
PU
FLT
GND
86
56
1010110
ACh
PU
FLT
PD
87
57
1010111
AEh
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Table 5.
I2C-bus slave address …continued
Hardware selectable input pins I2C-bus slave address for PCA9955B
AD2
AD1
AD0
Decimal Hexadecimal Binary (A[6:0]) Address (R/W = 0)
PU
FLT
FLT
88
58
1011000
B0h
PU
FLT
PU
89
59
1011001
B2h
PU
FLT
VDD
90
5A
1011010
B4h
PU
PU
GND
91
5B
1011011
B6h
PU
PU
PD
92
5C
1011100
B8h
PU
PU
FLT
93
5D
1011101
BAh
PU
PU
PU
94
5E
1011110
BCh
PU
PU
VDD
95
5F
1011111
BEh
PU
VDD
GND
96
60
1100000
C0h
PU
VDD
PD
97
61
1100001
C2h
PU
VDD
FLT
98
62
1100010
C4h
PU
VDD
PU
99
63
1100011
C6h
PU
VDD
VDD
100
64
1100100
C8h
VDD
GND
GND
101
65
1100101
CAh
VDD
GND
PD
102
66
1100110
CCh
VDD
GND
FLT
103
67
1100111
CEh
VDD
GND
PU
104
68
1101000
D0h
VDD
GND
VDD
105
69
1101001
D2h
VDD
PD
GND
106
6A
1101010
D4h
VDD
PD
PD
107
6B
1101011
D6h
VDD
PD
FLT
108
6C
1101100
D8h
VDD
PD
PU
109
6D
1101101
DAh
VDD
PD
VDD
110
6E
1101110
DCh
VDD
FLT
GND
111
6F
1101111
DEh
VDD
FLT
PD
112
70
1110000
E0h
VDD
FLT
FLT
113
71
1110001
E2h
VDD
FLT
PU
114
72
1110010
E4h
VDD
FLT
VDD
115
73
1110011
E6h
VDD
PU
GND
116
74
1110100
E8h
VDD
PU
PD
117
75
1110101
EAh
VDD
PU
FLT
118
76
1110110
ECh
VDD
PU
PU
119
77
1110111
EEh
VDD
PU
VDD
120
78
1111000[1]
F0h
79
1111001[1]
F2h
F4h
VDD
121
VDD
VDD
PD
122
7A
VDD
VDD
FLT
123
7B
1111011[1]
F6h
7C
1111100[1]
F8h
7D
1111101[1]
FAh
VDD
[1]
Product data sheet
GND
1111010[1]
VDD
PCA9955B
VDD
VDD
PU
VDD
VDD
124
125
See ‘Remark’ below.
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Remark: Reserved I2C-bus addresses must be used with caution since they can interfere
with:
•
•
•
•
‘reserved for future use’ I2C-bus addresses (0000 011, 1111 1XX)
slave devices that use the 10-bit addressing scheme (1111 0XX)
slave devices that are designed to respond to the General Call address (0000 000)
High-speed mode (Hs-mode) master code (0000 1XX)
VODYHDGGUHVV
$
$
$
$
$
$
$ 5:
DDI
(1) This slave address must match one of the 125 internal addresses as shown in Table 5
Fig 3.
PCA9955B slave address
The last bit of the address byte defines the operation to be performed. When set to logic 1
a read is selected, while a logic 0 selects a write operation.
7.1.2 LED All Call I2C-bus address
• Default power-up value (ALLCALLADR register): E0h or 1110 000X
• Programmable through I2C-bus (volatile programming)
• At power-up, LED All Call I2C-bus address is enabled. PCA9955B sends an ACK
when E0h (R/W = 0) or E1h (R/W = 1) is sent by the master.
See Section 7.3.11 “ALLCALLADR, LED All Call I2C-bus address” for more detail.
Remark: The default LED All Call I2C-bus address (E0h or 1110 000X) must not be used
as a regular I2C-bus slave address since this address is enabled at power-up. All of the
PCA9955Bs on the I2C-bus acknowledge the address if sent by the I2C-bus master.
7.1.3 LED Sub Call I2C-bus addresses
• 3 different I2C-bus addresses can be used
• Default power-up values:
– SUBADR1 register: ECh or 1110 110X
– SUBADR2 register: ECh or 1110 110X
– SUBADR3 register: ECh or 1110 110X
• Programmable through I2C-bus (volatile programming)
• At power-up, SUBADR1 is enabled while SUBADR2 and SUBADR3 I2C-bus
addresses are disabled.
Remark: At power-up SUBADR1 identifies this device as a 16-channel driver.
See Section 7.3.10 “LED Sub Call I2C-bus addresses for PCA9955B” for more detail.
Remark: The default LED Sub Call I2C-bus addresses may be used as regular I2C-bus
slave addresses as long as they are disabled.
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.2 Control register
Following the successful acknowledgement of the slave address, LED All Call address or
LED Sub Call address, the bus master sends a byte to the PCA9955B, which is stored in
the Control register.
The lowest 7 bits are used as a pointer to determine which register is accessed (D[6:0]).
The highest bit is used as Auto-Increment Flag (AIF).
This bit along with the MODE1 register bit 5 and bit 6 provide the Auto-Increment feature.
register address
AIF
D6
D5
D4
D3
D2
Auto-Increment Flag
D1
D0
002aad850
reset state = 80h
Remark: The Control register does not apply to the Software Reset I2C-bus address
Fig 4.
Control register
When the Auto-Increment Flag is set (AIF = logic 1), the seven low-order bits of the
Control register are automatically incremented after a read or write. This allows the user to
program the registers sequentially. Four different types of Auto-Increment are possible,
depending on AI1 and AI0 values of MODE1 register.
Table 6.
Auto-Increment options
AIF
AI1[1]
AI0[1] Function
0
0
0
no Auto-Increment
1
0
0
Auto-Increment for registers (00h to 43h). D[6:0] roll over to 00h after the last
register 43h is accessed.
1
0
1
Auto-Increment for individual brightness registers only (08h to 17h).
D[6:0] roll over to 08h after the last register (17h) is accessed.
1
1
0
Auto-Increment for MODE1 to IREF15 control registers (00h to 27h).
D[6:0] roll over to 00h after the last register (27h) is accessed.
1
1
1
Auto-Increment for global control registers and individual brightness registers
(06h to 17h). D[6:0] roll over to 06h after the last register (17h) is accessed.
[1]
AI1 and AI0 come from MODE1 register.
Remark: Other combinations not shown in Table 6 (AIF + AI[1:0] = 001b, 010b and 011b)
are reserved and must not be used for proper device operation.
AIF + AI[1:0] = 000b is used when the same register must be accessed several times
during a single I2C-bus communication, for example, changes the brightness of a single
LED. Data is overwritten each time the register is accessed during a write operation.
AIF + AI[1:0] = 100b is used when all the registers must be sequentially accessed, for
example, power-up programming.
AIF + AI[1:0] = 101b is used when the 16 LED drivers must be individually programmed
with different values during the same I2C-bus communication, for example, changing color
setting to another color setting.
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
AIF + AI[1:0] = 110b is used when MODE1 to IREF15 registers must be programmed with
different settings during the same I2C-bus communication.
AIF + AI[1:0] = 111b is used when the 16 LED drivers must be individually programmed
with different values in addition to global programming.
Only the 7 least significant bits D[6:0] are affected by the AIF, AI1 and AI0 bits.
When the Control register is written, the register entry point determined by D[6:0] is the
first register that will be addressed (read or write operation), and can be anywhere
between 00h and 49h (as defined in Table 7). When AIF = 1, the Auto-Increment Flag is
set and the rollover value at which the register increment stops and goes to the next one
is determined by AIF, AI1 and AI0. See Table 6 for rollover values. For example, if MODE1
register bit AI1 = 0 and AI0 = 1 and if the Control register = 1001 0000, then the register
addressing sequence is (in hexadecimal):
10  11  …  17  08  09  …  17  08  09  … as long as the master
keeps sending or reading data.
If MODE1 register bit AI1 = 0 and AI0 = 1 and if the Control register = 1010 0010, then the
register addressing sequence is (in hexadecimal):
22  23  …  43  00  01  …  17  08  09  … as long as the master
keeps sending or reading data.
If MODE1 register bit AI1 = 0 and AI0 = 1 and if the Control register = 1000 0101, then the
register addressing sequence is (in hexadecimal):
05  06  …  17  08  09  …  17  08  09  … as long as the master
keeps sending or reading data.
Remark: Writing to registers marked ‘not used’ returns NACK.
7.3 Register definitions
Table 7.
Register summary
Register
D6
number (hex)
D5
D4
D3
D2
D1
D0
Name
Type
00h
0
0
0
0
0
0
0
MODE1
read/write Mode register 1
01h
0
0
0
0
0
0
1
MODE2
read/write Mode register 2
02h
0
0
0
0
0
1
0
LEDOUT0
read/write LED output state 0
03h
0
0
0
0
0
1
1
LEDOUT1
read/write LED output state 1
04h
0
0
0
0
1
0
0
LEDOUT2
read/write LED output state 2
05h
0
0
0
0
1
0
1
LEDOUT3
read/write LED output state 3
06h
0
0
0
0
1
1
0
GRPPWM
read/write group duty cycle control
07h
0
0
0
0
1
1
1
GRPFREQ
read/write group frequency
08h
0
0
0
1
0
0
0
PWM0
read/write brightness control LED0
09h
0
0
0
1
0
0
1
PWM1
read/write brightness control LED1
0Ah
0
0
0
1
0
1
0
PWM2
read/write brightness control LED2
0Bh
0
0
0
1
0
1
1
PWM3
read/write brightness control LED3
0Ch
0
0
0
1
1
0
0
PWM4
read/write brightness control LED4
0Dh
0
0
0
1
1
0
1
PWM5
read/write brightness control LED5
0Eh
0
0
0
1
1
1
0
PWM6
read/write brightness control LED6
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Function
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Table 7.
Register summary …continued
Register
D6
number (hex)
D5
D4
D3
D2
D1
D0
Name
Type
Function
0Fh
0
0
0
1
1
1
1
PWM7
read/write brightness control LED7
10h
0
0
1
0
0
0
0
PWM8
read/write brightness control LED8
11h
0
0
1
0
0
0
1
PWM9
read/write brightness control LED9
12h
0
0
1
0
0
1
0
PWM10
read/write brightness control LED10
13h
0
0
1
0
0
1
1
PWM11
read/write brightness control LED11
14h
0
0
1
0
1
0
0
PWM12
read/write brightness control LED12
15h
0
0
1
0
1
0
1
PWM13
read/write brightness control LED13
16h
0
0
1
0
1
1
0
PWM14
read/write brightness control LED14
17h
0
0
1
0
1
1
1
PWM15
read/write brightness control LED15
18h
0
0
1
1
0
0
0
IREF0
read/write output gain control register 0
19h
0
0
1
1
0
0
1
IREF1
read/write output gain control register 1
1Ah
0
0
1
1
0
1
0
IREF2
read/write output gain control register 2
1Bh
0
0
1
1
0
1
1
IREF3
read/write output gain control register 3
1Ch
0
0
1
1
1
0
0
IREF4
read/write output gain control register 4
1Dh
0
0
1
1
1
0
1
IREF5
read/write output gain control register 5
1Eh
0
0
1
1
1
1
0
IREF6
read/write output gain control register 6
1Fh
0
0
1
1
1
1
1
IREF7
read/write output gain control register 7
20h
0
1
0
0
0
0
0
IREF8
read/write output gain control register 8
21h
0
1
0
0
0
0
1
IREF9
read/write output gain control register 9
22h
0
1
0
0
0
1
0
IREF10
read/write output gain control register 10
23h
0
1
0
0
0
1
1
IREF11
read/write output gain control register 11
24h
0
1
0
0
1
0
0
IREF12
read/write output gain control register 12
25h
0
1
0
0
1
0
1
IREF13
read/write output gain control register 13
26h
0
1
0
0
1
1
0
IREF14
read/write output gain control register 14
27h
0
1
0
0
1
1
1
IREF15
read/write output gain control register 15
28h
0
1
0
1
0
0
0
RAMP_RATE_GRP0
read/write ramp enable and rate control
for group 0
29h
0
1
0
1
0
0
1
STEP_TIME_GRP0
read/write step time control for group 0
2Ah
0
1
0
1
0
1
0
HOLD_CNTL_GRP0
read/write hold ON/OFF time control for
group 0
2Bh
0
1
0
1
0
1
1
IREF_GRP0
read/write output gain control for group 0
2Ch
0
1
0
1
1
0
0
RAMP_RATE_GRP1
read/write ramp enable and rate control
for group 1
2Dh
0
1
0
1
1
0
1
STEP_TIME_GRP1
read/write step time control for group 1
2Eh
0
1
0
1
1
1
0
HOLD_CNTL_GRP1
read/write hold ON/OFF time control for
group 1
2Fh
0
1
0
1
1
1
1
IREF_GRP1
read/write output gain control for group 1
30h
0
1
1
0
0
0
0
RAMP_RATE_GRP2
read/write ramp enable and rate control
for group 2
31h
0
1
1
0
0
0
1
STEP_TIME_GRP2
read/write step time control for group 2
32h
0
1
1
0
0
1
0
HOLD_CNTL_GRP2
read/write hold ON/OFF time control for
group 2
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Table 7.
Register summary …continued
Register
D6
number (hex)
D5
D4
D3
D2
D1
D0
Name
Type
33h
0
1
1
0
0
1
1
IREF_GRP2
read/write output gain control for group 2
34h
0
1
1
0
1
0
0
RAMP_RATE_GRP3
read/write ramp enable and rate control
for group 3
35h
0
1
1
0
1
0
1
STEP_TIME_GRP3
read/write step time control for group 3
36h
0
1
1
0
1
1
0
HOLD_CNTL_GRP3
read/write hold ON/OFF time control for
group 3
37h
0
1
1
0
1
1
1
IREF_GRP3
read/write output gain control for group 3
38h
0
1
1
1
0
0
0
GRAD_MODE_SEL0
read/write gradation mode select register
for channel 7 to channel 0
39h
0
1
1
1
0
0
1
GRAD_MODE_SEL1
read/write gradation mode select register
for channel 15 to channel 8
3Ah
0
1
1
1
0
1
0
GRAD_GRP_SEL0
read/write gradation group select for
channel 3 to channel 0
3Bh
0
1
1
1
0
1
1
GRAD_GRP_SEL1
read/write gradation group select for
channel 7 to channel 4
3Ch
0
1
1
1
1
0
0
GRAD_GRP_SEL2
read/write gradation group select for
channel 11 to channel 8
3Dh
0
1
1
1
1
0
1
GRAD_GRP_SEL3
read/write gradation group select for
channel 15 to channel 12
3Eh
0
1
1
1
1
1
0
GRAD_CNTL
read/write gradation control register for all
four groups
3Fh
0
1
1
1
1
1
1
OFFSET
read/write Offset/delay on LEDn outputs
40h
1
0
0
0
0
0
0
SUBADR1
read/write I2C-bus subaddress 1
41h
1
0
0
0
0
0
1
SUBADR2
read/write I2C-bus subaddress 2
42h
1
0
0
0
0
1
0
SUBADR3
read/write I2C-bus subaddress 3
43h
1
0
0
0
0
1
1
ALLCALLADR
read/write All Call I2C-bus address
44h
1
0
0
0
1
0
0
PWMALL
write only
brightness control for all LEDn
45h
1
0
0
0
1
0
1
IREFALL
write only
output gain control for all
registers IREF0 to IREF15
46h
1
0
0
0
1
1
0
EFLAG0
read only
output error flag 0
47h
1
0
0
0
1
1
1
EFLAG1
read only
output error flag 1
48h
1
0
0
1
0
0
0
EFLAG2
read only
output error flag 2
49h
1
0
0
1
0
0
1
EFLAG3
read only
output error flag 3
4Ah to 7Fh
-
-
-
-
-
-
-
reserved
read only
not used[1]
[1]
Function
Reserved registers should not be written to and will always read back as zeros.
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.1 MODE1 — Mode register 1
Table 8.
MODE1 - Mode register 1 (address 00h) bit description
Legend: * default value.
Bit
Symbol
Access
Value
Description
7
AIF
read only
0
Register Auto-Increment disabled.
1*
Register Auto-Increment enabled.
0*
Auto-Increment bit 1 = 0. Auto-increment range as defined in Table 6.
1
Auto-Increment bit 1 = 1. Auto-increment range as defined in Table 6.
0*
Auto-Increment bit 0 = 0. Auto-increment range as defined in Table 6.
1
Auto-Increment bit 0 = 1. Auto-increment range as defined in Table 6.
0*
Normal mode[1].
1
Low power mode. Oscillator off[2][3].
0
PCA9955B does not respond to I2C-bus subaddress 1.
1*
PCA9955B responds to I2C-bus subaddress 1.
0*
PCA9955B does not respond to I2C-bus subaddress 2.
1
PCA9955B responds to I2C-bus subaddress 2.
0*
PCA9955B does not respond to I2C-bus subaddress 3.
1
PCA9955B responds to I2C-bus subaddress 3.
0
PCA9955B does not respond to LED All Call I2C-bus address.
1*
PCA9955B responds to LED All Call I2C-bus address.
6
AI1
5
AI0
4
SLEEP
3
SUB1
2
SUB2
1
SUB3
0
[1]
ALLCALL
R/W
R/W
R/W
R/W
R/W
R/W
R/W
It takes 500 s max. for the oscillator to be up and running once SLEEP bit has been set to logic 0. Timings on LEDn outputs are not
guaranteed if PWMx, GRPPWM or GRPFREQ registers are accessed within the 500 s window.
[2]
No blinking, dimming or gradation control is possible when the oscillator is off.
[3]
The device must be reset if the LED driver output state is set to LDRx=11 after the device is set back to Normal mode.
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.2 MODE2 — Mode register 2
Table 9.
MODE2 - Mode register 2 (address 01h) bit description
Legend: * default value.
Bit
Symbol
Access
7
OVERTEMP
read only
6
5
4
3
2
ERROR
DMBLNK
CLRERR
OCH
EXP_EN
read only
R/W
write only
R/W
R/W
Value
Description
0*
O.K.
1
overtemperature condition
0*
no error at LED outputs
1
any open or short-circuit detected in
error flag registers (EFLAGn)
0*
group control = dimming
1
group control = blinking
0*
self clear after write ‘1’
1
Write ‘1’ to clear all error status bits in EFLAGn
register and ERROR (bit 6). The EFLAGn and
ERROR bit sets to ‘1’ if open or short-circuit is
detected again.
0*
outputs change on STOP condition
1
outputs change on ACK
0*
linear adjustment for gradation control
1
exponential adjustment for gradation control
1
-
read only
0*
reserved
0
-
read only
1*
reserved
Brightness adjustment for gradation control is either linear or exponential by setting the
EXP_EN bit as shown in Figure 5. When EXP_EN = 0, linear adjustment scale is used.
When EXP_EN = 1, exponential scale is used.
DDK
,5()B287
(;3B(1 (;3B(1 ,5()B,1
Fig 5.
PCA9955B
Product data sheet
Linear and exponential adjustment curves
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.3 LEDOUT0 to LEDOUT3, LED driver output state
Table 10.
LEDOUT0 to LEDOUT3 - LED driver output state registers (address 02h to 05h)
bit description
Legend: * default value.
Address
Register
Bit
Symbol
Access
Value
Description
02h
LEDOUT0
7:6
LDR3
R/W
10*
LED3 output state control
5:4
LDR2
R/W
10*
LED2 output state control
3:2
LDR1
R/W
10*
LED1 output state control
1:0
LDR0
R/W
10*
LED0 output state control
7:6
LDR7
R/W
10*
LED7 output state control
5:4
LDR6
R/W
10*
LED6 output state control
3:2
LDR5
R/W
10*
LED5 output state control
1:0
LDR4
R/W
10*
LED4 output state control
7:6
LDR11
R/W
10*
LED11 output state control
5:4
LDR10
R/W
10*
LED10 output state control
3:2
LDR9
R/W
10*
LED9 output state control
1:0
LDR8
R/W
10*
LED8 output state control
7:6
LDR15
R/W
10*
LED15 output state control
5:4
LDR14
R/W
10*
LED14 output state control
3:2
LDR13
R/W
10*
LED13 output state control
1:0
LDR12
R/W
10*
LED12 output state control
03h
04h
05h
LEDOUT1
LEDOUT2
LEDOUT3
LDRx = 00 — LED driver x is off (x = 0 to 15).
LDRx = 01 — LED driver x is fully on (individual brightness and group dimming/blinking
not controlled). The OE pin can be used as external dimming/blinking control in this state.
LDRx = 10 — LED driver x individual brightness can be controlled through its PWMx
register (default power-up state) or PWMALL register for all LEDn outputs.
LDRx = 11 — LED driver x individual brightness and group dimming/blinking can be
controlled through its PWMx register and the GRPPWM registers.
Remark: Setting the device in low power mode while being on group dimming/blinking
mode may cause the LED output state to be in an unknown state after the device is set
back to normal mode. The device must be reset and all register values reprogrammed.
7.3.4 GRPPWM, group duty cycle control
Table 11. GRPPWM - Group brightness control register (address 06h) bit description
Legend: * default value
Address
Register
Bit
Symbol
Access
Value
Description
06h
GRPPWM
7:0
GDC[7:0]
R/W
1111 1111*
GRPPWM register
When DMBLNK bit (MODE2 register) is programmed with logic 0, a 122 Hz fixed
frequency signal is superimposed with the 31.25 kHz individual brightness control signal.
GRPPWM is then used as a global brightness control allowing the LED outputs to be
dimmed with the same value. The value in GRPFREQ is then a ‘Don’t care’.
PCA9955B
Product data sheet
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NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
General brightness for the 16 outputs is controlled through 255 linear steps from 00h
(0 % duty cycle = LED output off) to FFh (99.6 % duty cycle = maximum brightness).
Applicable to LED outputs programmed with LDRx = 11 (LEDOUT0 to LEDOUT3
registers).
When DMBLNK bit is programmed with logic 1, GRPPWM and GRPFREQ registers
define a global blinking pattern, where GRPFREQ contains the blinking period (from
67 ms to 16.8 s) and GRPPWM the duty cycle (ON/OFF ratio in %).
GDC  7:0 
duty cycle = -------------------------256
(1)
7.3.5 GRPFREQ, group frequency
Table 12. GRPFREQ - Group frequency register (address 07h) bit description
Legend: * default value.
Address
Register
Bit
Symbol
Access
Value
Description
07h
GRPFREQ
7:0
GFRQ[7:0]
R/W
0000 0000*
GRPFREQ register
GRPFREQ is used to program the global blinking period when DMBLNK bit (MODE2
register) is equal to 1. Value in this register is a ‘Don’t care’ when DMBLNK = 0.
Applicable to LED outputs programmed with LDRx = 11 (LEDOUT0 to LEDOUT3
registers).
Blinking period is controlled through 256 linear steps from 00h (67 ms, frequency 15 Hz)
to FFh (16.8 s).
GFRQ  7:0  + 1
global blinking period = ----------------------------------------  s 
15.26
(2)
7.3.6 PWM0 to PWM15, individual brightness control
Table 13. PWM0 to PWM15 - PWM registers 0 to 15 (address 08h to 17h) bit description
Legend: * default value.
PCA9955B
Product data sheet
Address
Register
Bit
Symbol
Access Value
08h
PWM0
7:0
IDC0[7:0]
R/W
0000 0000* PWM0 Individual Duty Cycle
09h
PWM1
7:0
IDC1[7:0]
R/W
0000 0000* PWM1 Individual Duty Cycle
0Ah
PWM2
7:0
IDC2[7:0]
R/W
0000 0000* PWM2 Individual Duty Cycle
0Bh
PWM3
7:0
IDC3[7:0]
R/W
0000 0000* PWM3 Individual Duty Cycle
0Ch
PWM4
7:0
IDC4[7:0]
R/W
0000 0000* PWM4 Individual Duty Cycle
0Dh
PWM5
7:0
IDC5[7:0]
R/W
0000 0000* PWM5 Individual Duty Cycle
0Eh
PWM6
7:0
IDC6[7:0]
R/W
0000 0000* PWM6 Individual Duty Cycle
0Fh
PWM7
7:0
IDC7[7:0]
R/W
0000 0000* PWM7 Individual Duty Cycle
10h
PWM8
7:0
IDC8[7:0]
R/W
0000 0000* PWM8 Individual Duty Cycle
11h
PWM9
7:0
IDC9[7:0]
R/W
0000 0000* PWM9 Individual Duty Cycle
12h
PWM10
7:0
IDC10[7:0]
R/W
0000 0000* PWM10 Individual Duty Cycle
13h
PWM11
7:0
IDC11[7:0]
R/W
0000 0000* PWM11 Individual Duty Cycle
14h
PWM12
7:0
IDC12[7:0]
R/W
0000 0000* PWM12 Individual Duty Cycle
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Description
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Table 13.
PWM0 to PWM15 - PWM registers 0 to 15 (address 08h to 17h) bit description
…continued
Address
Register
Bit
Symbol
Access Value
Description
15h
PWM13
7:0
IDC13[7:0]
R/W
0000 0000* PWM13 Individual Duty Cycle
16h
PWM14
7:0
IDC14[7:0]
R/W
0000 0000* PWM14 Individual Duty Cycle
17h
PWM15
7:0
IDC15[7:0]
R/W
0000 0000* PWM15 Individual Duty Cycle
A 31.25 kHz fixed frequency signal is used for each output. Duty cycle is controlled
through 255 linear steps from 00h (0 % duty cycle = LED output off) to FEh
(99.2 % duty cycle = LED output at maximum brightness) and FFh (100 % duty cycle =
LED output completed ON). Applicable to LED outputs programmed with LDRx = 10 or 11
(LEDOUT0 to LEDOUT3 registers).
IDCx  7:0 
duty cycle = --------------------------256
(3)
Remark: The first lower end 8 steps of PWM and the last (higher end) steps of PWM will
not have effective brightness control of LEDs due to edge rate control of LED output pins.
7.3.7 IREF0 to IREF15, LED output current value registers
These registers reflect the gain settings for output current for LED0 to LED15.
Table 14.
IREF0 to IREF15 - LED output gain control registers (address 18h to 27h)
bit description
Legend: * default value.
PCA9955B
Product data sheet
Address
Register
Bit
Access
Value
Description
18h
IREF0
7:0
R/W
00h*
LED0 output current setting
19h
IREF1
7:0
R/W
00h*
LED1 output current setting
1Ah
IREF2
7:0
R/W
00h*
LED2 output current setting
1Bh
IREF3
7:0
R/W
00h*
LED3 output current setting
1Ch
IREF4
7:0
R/W
00h*
LED4 output current setting
1Dh
IREF5
7:0
R/W
00h*
LED5 output current setting
1Eh
IREF6
7:0
R/W
00h*
LED6 output current setting
1Fh
IREF7
7:0
R/W
00h*
LED7 output current setting
20h
IREF8
7:0
R/W
00h*
LED8 output current setting
21h
IREF9
7:0
R/W
00h*
LED9 output current setting
22h
IREF10
7:0
R/W
00h*
LED10 output current setting
23h
IREF11
7:0
R/W
00h*
LED11 output current setting
24h
IREF12
7:0
R/W
00h*
LED12 output current setting
25h
IREF13
7:0
R/W
00h*
LED13 output current setting
26h
IREF14
7:0
R/W
00h*
LED14 output current setting
27h
IREF15
7:0
R/W
00h*
LED15 output current setting
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Rev. 2 — 20 November 2015
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.8 Gradation control
Gradation control is designed to use four independent groups of registers to program the
full cycle of the gradation timing to implement on each selected channel. Each group has
four registers to define the ramp rate, step time, hold ON/OFF time, and final hold ON
current, as shown in Figure 6.
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VHWLQ
,5()B*53[
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7
7
7
7
7
WLPHVHFRQG
IXOOF\FOH
DDK
Fig 6.
Gradation timing
• The ‘final’ and ‘hold ON’ current is defined in IREF_GRPx register value  (225 A if
REXT = 1 k, or 112.5 A if REXT = 2 k).
• Ramp rate value and enable/disable ramp operation is defined in
RAMP_RATE_GRPx register.
• Total number of ramp steps (or level changes) is calculated as
‘IREF_GRPx value’  ‘ramp rate value in RAMP_RATE_GRPx’. Rounds a number up
to the next integer if the total number is not an integer.
• Time for each step is calculated as ‘cycle time’  ‘multiple factor’ bits in
STEP_TIME_GRPx register. Minimum time for one step is 0.5 ms (0.5 ms  1) and
maximum time is 512 ms (8 ms  64).
• The ramp-up or ramp-down time (T1 or T3) is calculated as
‘(total steps + 1)’  ‘step time’.
• Hold ON or OFF time (T2 or T4) is defined in HOLD_CNTL_GRPx register in the
range of 0/0.25/0.5/0.75/1/2/4/6 seconds.
• Gradation start or stop with single shot mode (one full cycle only) or continuous mode
(repeat full cycle) is defined in the GRAD_CNTL register for all groups.
• Each channel can be assigned to one of these four groups in the GRAD_GRP_SELx
register.
• Each channel can set either normal mode or gradation mode operation in the
GRAD_MODE_SELx register.
To enable the gradation operation, the following steps are required:
1. Program all gradation control registers except the gradation start bit in GRAD_CNTL
register.
2. Program either LDRx = 01 (LED fully ON mode) only, or LDRx = 10 or 11 (PWM
control mode) with individual brightness control PWMx register for duty cycle.
PCA9955B
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
3. Program output current value IREFx register to non-zero, which will enable LED
output.
4. Set the gradation start bit in GRAD_CNTL register for enabling gradation operation.
7.3.8.1
RAMP_RATE_GRP0 to RAMP_RATE_GRP3, ramp rate control registers
Table 15.
RAMP_RATE_GRP[0:3] - Ramp enable and rate control registers (address 28h,
2Ch, 30h, 34h) for each group bit description
Legend: * default value.
Address
Register
Bit
Access
Value
Description
28h
RAMP_RATE_GRP0
7
R/W
0*
Ramp-up disable
2Ch
RAMP_RATE_GRP1
1
Ramp-up enable
30h
RAMP_RATE_GRP2
6
R/W
0*
Ramp-down disable
34h
RAMP_RATE_GRP3
1
Ramp-down enable
0x00*
Ramp rate value per step is defined
from 1 (00h) to 64 (3Fh)[1][2]
5:0
7.3.8.2
R/W
[1]
Total number of ramp steps is defined as ‘IREF_GRP[7:0]’  ‘ramp_rate[5:0]’. (Round up to next integer if it
is not an integer number.)
[2]
Per step current increment or decrement is calculated by the (ramp_rate  Iref), where the Iref reference
current is 112.5 A (REXT = 2 k) or 225 A (REXT = 1 k).
STEP_TIME_GRP0 to STEP_TIME_GRP3, step time control registers
Table 16.
STEP_TIME_GRP[0:3] - Step time control registers (address 29h, 2Dh, 31h, 35h)
for each group bit description
Legend: * default value.
Address
Register
Bit
Access
Value
Description
29h
STEP_TIME_GRP0
7
read only
0*
reserved
2Dh
STEP_TIME_GRP1
6
R/W
0*
Cycle time is set to 0.5 ms
31h
STEP_TIME_GRP2
1
Cycle time is set to 8 ms
35h
STEP_TIME_GRP3
5:0
R/W
0x00*
Multiple factor per step, the
multiple factor is defined from
1 (00h) to 64 (3Fh)[1]
[1]
PCA9955B
Product data sheet
Step time = cycle time (0.5 ms or 8 ms)  multiple factor (1 ~ 64); minimum step time is 0.5 ms and
maximum step time is 512 ms.
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.8.3
HOLD_CNTL_GRP0 to HOLD_CNTL_GRP3, hold ON and OFF control registers
Table 17.
HOLD_CNTL_GRP[0:3] - Hold ON and OFF enable and time control registers
(address 2Ah, 2Eh, 32h, 36h) for each group bit description
Legend: * default value.
Address
Register
Bit
Access
Value
Description
2Ah
HOLD_CNTL_GRP0
7
R/W
0*
Hold ON disable
2Eh
HOLD_CNTL_GRP1
1
Hold ON enable
32h
HOLD_CNTL_GRP2
0*
Hold OFF disable
36h
HOLD_CNTL_GRP3
1
Hold OFF enable
000*
Hold ON time select:[1]
6
5:3
R/W
R/W
000: 0 s
001: 0.25 s
010: 0.5 s
011: 0.75 s
100: 1 s
101: 2 s
110: 4 s
111: 6 s
2:0
R/W
000*
Hold OFF time select:[1]
000: 0 s
001: 0.25 s
010: 0.5 s
011: 0.75 s
100: 1 s
101: 2 s
110: 4 s
111: 6 s
[1]
7.3.8.4
Hold ON or OFF minimum time is 0 s and maximum time is 6 s
IREF_GRP0 to IREF_GRP3, output gain control
Table 18.
IREF_GRP[0:3] - Final and hold ON output gain setting registers
(address 2Bh, 2Fh, 33h, 37h) for each group bit description
Legend: * default value.
Address
Register
Bit
Access
Value
Description
2Bh
IREF_GRP0
7:0
R/W
00h*
2Fh
IREF_GRP1
Final ramp-up and hold ON output
current gain setting[1]
33h
IREF_GRP2
37h
IREF_GRP3
[1]
PCA9955B
Product data sheet
Output current = Iref  IREF_GRPx[7:0], where Iref is reference current. Iref = 112.5 A if REXT = 2 k,
or Iref = 225 A if REXT = 1 k
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.8.5
GRAD_MODE_SEL0 to GRAD_MODE_SEL1, Gradation mode select registers
Table 19.
GRAD_MODE_SEL[0:1] - Gradation mode select register for channel 15 to
channel 0 (address 38h, 39h) bit description
Legend: * default value.
Address
Register
38h
GRAD_MODE_SEL0 7:0
39h
7.3.8.6
Bit
GRAD_MODE_SEL1 7:0
Access
Value
Description[1][2]
R/W
00*
Normal operation mode for
channel 7 to channel 0
FFh
Gradation operation mode for
channel 7 to channel 0
00*
Normal operation mode for
channel 15 to channel 8
FFh
Gradation operation mode for
channel 15 to channel 8
R/W
[1]
Each bit represents one channel that can set either 0 for normal mode (use IREFx to set individual LED
output current), or 1 for gradation mode (use IREF_GRPx to set group LEDs output current.).
[2]
In gradation mode, it only affects the source of the IREF current level and does not affect the PWMx
operation or LEDOUTx registers’ function. It is possible to use the gradation feature, individual PWMx and
group PWM simultaneously.
GRAD_GRP_SEL0 to GRAD_GRP_SEL3, Gradation group select registers
Table 20.
GRAD_GRP_SEL[0:3] - Gradation group select register for channel 15 to
channel 0 (address 3Ah, 3Bh, 3Ch, 3Dh) bit description
Legend: * default value.
Access
Value Description[1]
GRAD_GRP_SEL0 7:6
R/W
00*
Gradation group select for LED3 output
5:4
R/W
00*
Gradation group select for LED2 output
3:2
R/W
00*
Gradation group select for LED1 output
Address Register
3Ah
3Bh
3Ch
3Dh
[1]
PCA9955B
Product data sheet
Bit
1:0
R/W
00*
Gradation group select for LED0 output
GRAD_GRP_SEL1 7:6
R/W
01*
Gradation group select for LED7 output
5:4
R/W
01*
Gradation group select for LED6 output
3:2
R/W
01*
Gradation group select for LED5 output
1:0
R/W
01*
Gradation group select for LED4 output
GRAD_GRP_SEL2 7:6
R/W
10*
Gradation group select for LED11 output
5:4
R/W
10*
Gradation group select for LED10 output
3:2
R/W
10*
Gradation group select for LED9 output
1:0
R/W
10*
Gradation group select for LED8 output
GRAD_GRP_SEL3 7:6
R/W
11*
Gradation group select for LED15 output
5:4
R/W
11*
Gradation group select for LED14 output
3:2
R/W
11*
Gradation group select for LED13 output
1:0
R/W
11*
Gradation group select for LED12 output
LED[3:0] outputs default assigned to group 0; LED[7:4] outputs default assigned to group 1;
LED[11:8] outputs default assigned to group 2; LED[15:12] outputs default assigned to group 3.
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.8.7
GRAD_CNTL, Gradation control register
Table 21.
GRAD_CNTL - Gradation control register for group 3 to group 0 (address 3Eh)
bit description
Legend: * default value.
Address
Register
Bit
Access
Value
Description
3Eh
GRAD_CNTL
7
R/W
0*
Gradation stop or done for group 3[1]
1
Gradation start for group 3[2]
0*
Single shot operation for group 3
1
Continuous operation for group 3
0*
Gradation stop or done for group 2[1]
1
Gradation start for group 2[2]
0*
Single shot operation for group 2
1
Continuous operation for group 2
0*
Gradation stop or done for group 1[1]
1
Gradation start for group 1[2]
0*
Single shot operation for group 1
1
Continuous operation for group 1
0*
Gradation stop or done for group 0[1]
1
Gradation start for group 0[2]
0*
Single shot operation for group 0
1
Continuous operation for group 0
6
5
4
3
2
1
0
PCA9955B
Product data sheet
R/W
R/W
R/W
R/W
R/W
R/W
R/W
[1]
When the gradation operation is forced to stop, the output current stops immediately and is frozen at the
last output level.
[2]
This bit will be self-cleared when single mode is completed, and writing 0 to this bit will force to stop the
gradation operation when single mode is not completed or continuous mode is running.
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Rev. 2 — 20 November 2015
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26 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.8.8
Ramp control — equation and calculation example
IREF_GRPx
(max. = 255)
225 μA × 250 = 56.25 mA
250
200
150
s1
100
50
(step time)
(32 ms)
0
End with
current zero
t1
time
ramp-up
hold ON
ramp-down
hold OFF
(T = 192 ms)
(0.25 s)
(T = 192 ms)
(0.5 s)
Start from
current zero
Fig 7.
(step current)
(11.25 mA)
full cycle
002aah637
Ramp calculation example 1
• t1 (step time) = cycle time  multiple factor, where:
– Cycle time = 0.5 ms (fast ramp) or 8 ms (slow ramp) in STEP_TIME_GRPx[6]
– Multiple factor = 6-bit, from 1 (00h) to 64 (3Fh) counts in STEP_TIME_GRPx[5:0]
• s1 (step current) = ramp_rate  Iref, where:
– ramp_rate = 6-bit, from 1 (00h) to 64 (3Fh) counts in RAMP_RATE_GRPx[5:0]
– Iref = reference current either 112.5 A if REXT = 2 k, or 225 A if REXT = 1 k
• S (total steps) = (IREF_GRPx / ramp_rate), where:
– IREF_GRPx = output current gain setting, 8-bit, up to 255 counts
– ramp_rate = 6-bit, up to 64 counts in RAMP_RATE_GRPx[5:0]
– If it is not an integer, then round up to next integer number.
• T (ramp time) = (S (total steps) + 1)  t1 (step time)
– Ramp-up time starts from zero current and ends at the maximum current
– Ramp-down time starts from the maximum current and ends at the zero current
Calculation example 1 (Figure 7):
• Assumption:
– Iref = 225 A if REXT = 1 k
– Output hold ON current = 225 A  250 = 56.25 mA (IREF_GRPx[7:0] = FAh)
– Cycle time = 0.5 ms (STEP_TIME_GRPx[6] = 0)
– Multiple factor = 64 (STEP_TIME_GRPx[5:0] = 3Fh)
– Ramp rate = 50 (RAMP_RATE_GRPx[5:0] = 31h)
– Hold ON = 0.25 s (HOLD_CNTL_GRPx[5:3] = 001)
– Hold OFF = 0.5 s (HOLD_CNTL_GRPx[2:0] = 010)
• t1 (step time) = cycle time (0.5 ms)  multiple (64) = 32 ms
• Step current = ramp_rate  Iref = 50  225 A = 11.25 mA
PCA9955B
Product data sheet
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Rev. 2 — 20 November 2015
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27 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
• S (total steps) = (IREF_GRPx  ramp_rate) = (250  50) = 5 steps
• T (ramp time) = (S + 1)  t1 = 6  32 ms = 192 ms
IREF_GRPx
(max. = 255)
240
(54 mA)
200
t1
(step time)
(32 ms)
150
190
140
s1
100
(step current)
90
50
(11.25 mA)
0
40
time
ramp-up
hold ON
ramp-down
hold OFF
(T = 192 ms)
(0.25 s)
(T = 192 ms)
(0.5 s)
full cycle
Fig 8.
002aah674
Ramp calculation example 2
Calculation example 2:
• Assumption:
– Iref = 225 A if REXT = 1 k
– Output hold ON current = 225 A  240 = 54 mA (IREF_GRPx[7:0] = F0h)
– Cycle time = 0.5 ms (STEP_TIME_GRPx[6] = 0)
– Multiple factor = 64 (STEP_TIME_GRPx[5:0] = 3Fh)
– Ramp rate = 50 (RAMP_RATE_GRPx[5:0] = 31h)
– Hold ON = 0.25 s (HOLD_CNTL_GRPx[5:3] = 001)
– Hold OFF = 0.5 s (HOLD_CNTL_GRPx[2:0] = 010)
• t1 (step time) = cycle time (0.5 ms)  multiple (64) = 32 ms
• Step current = ramp_rate  Iref = 50  225 A = 11.25 mA (except the last one)
• S (total steps) = IREF_GRPx  ramp_rate = 240  50 = 4.8 steps (round up to next
integer) = 5 steps
• T (ramp time) = (S + 1)  t1 = 6  32 ms = 192 ms
PCA9955B
Product data sheet
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Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
28 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
HQDEOHELW
5DPS83
HQDEOHELW
+ROG21
HQDEOHELW
5DPS'2:1
HQDEOHELW
+ROG2))
6LQJOHVKRWZDYHIRUP
&RQWLQXRXVZDYHIRUP
ZDYHIRUPZKHQLQLWLDOFXUUHQWLVQRW]HUR
WKHPRPHQWZKHQ67$57ELWUHDGEDFN
FKDQJHVWRVLQJOHVKRWVHTXHQFHHQGV
Fig 9.
PCA9955B
Product data sheet
DDK
Gradation output waveform in single shot or continuous mode
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.9 OFFSET — LEDn output delay offset register
Table 22. OFFSET - LEDn output delay offset register (address 3Fh) bit description
Legend: * default value.
Address
Register
3Fh
OFFSET
Bit
Access
Value
Description
7:4
read only 0000*
not used
3:0
R/W
LEDn output delay offset factor
1000*
The PCA9955B can be programmed to have turn-on delay between LED outputs. This
helps to reduce peak current for the VDD supply and reduces EMI.
The order in which the LED outputs are enabled will always be the same (channel 0 will
enable first and channel 15 will enable last).
OFFSET control register bits [3:0] determine the delay used between the turn-on times as
follows:
0000 = no delay between outputs (all on, all off at the same time)
0001 = delay of 1 clock cycle (125 ns) between successive outputs
0010 = delay of 2 clock cycles (250 ns) between successive outputs
0011 = delay of 3 clock cycles (375 ns) between successive outputs
:
1111 = delay of 15 clock cycles (1.875 s) between successive outputs
Example: If the value in the OFFSET register is 1000 the corresponding delay =
8  125 ns = 1 s delay between successive outputs.
channel 0 turns on at time 0 s
channel 1 turns on at time 1 s
channel 2 turns on at time 2 s
channel 3 turns on at time 3 s
channel 4 turns on at time 4 s
channel 5 turns on at time 5 s
channel 6 turns on at time 6 s
channel 7 turns on at time 7 s
channel 8 turns on at time 8 s
channel 9 turns on at time 9 s
channel 10 turns on at time 10 s
channel 11 turns on at time 11 s
channel 12 turns on at time 12 s
channel 13 turns on at time 13 s
channel 14 turns on at time 14 s
channel 15 turns on at time 15 s
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.10 LED Sub Call I2C-bus addresses for PCA9955B
SUBADR1 to SUBADR3 - I2C-bus subaddress registers 1 to 3 (address 40h to
42h) bit description
Legend: * default value.
Table 23.
Address
Register
Bit
Symbol
Access Value
Description
40h
SUBADR1
7:1
A1[7:1]
R/W
1110 110*
I2C-bus subaddress 1
0
A1[0]
R only
0*
reserved
A2[7:1]
R/W
1110 110*
I2C-bus subaddress 2
41h
SUBADR2
7:1
0
A2[0]
R only
0*
reserved
42h
SUBADR3
7:1
A3[7:1]
R/W
1110 110*
I2C-bus subaddress 3
0
A3[0]
R only
0*
reserved
Default power-up values are ECh, ECh, ECh. At power-up, SUBADR1 is enabled while
SUBADR2 and SUBADR3 are disabled. The power-up default bit subaddress of ECh
indicates that this device is a 16-channel LED driver.
All three subaddresses are programmable. Once subaddresses have been programmed
to their right values, SUBx bits need to be set to logic 1 in order to have the device
acknowledging these addresses (MODE1 register) (0). When SUBx is set to logic 1, the
corresponding I2C-bus subaddress can be used during either an I2C-bus read or write
sequence.
7.3.11 ALLCALLADR, LED All Call I2C-bus address
ALLCALLADR - LED All Call I2C-bus address register (address 43h) bit
description
Legend: * default value.
Table 24.
Address
Register
Bit
Symbol
Access Value
Description
43h
ALLCALLADR
7:1
AC[7:1]
R/W
1110 000*
ALLCALL I2C-bus
address register
0
AC[0]
R only
0*
reserved
The LED All Call I2C-bus address allows all the PCA9955Bs on the bus to be programmed
at the same time (ALLCALL bit in register MODE1 must be equal to logic 1 [power-up
default state]). This address is programmable through the I2C-bus and can be used during
either an I2C-bus read or write sequence. The register address can also be programmed
as a Sub Call.
Only the 7 MSBs representing the All Call I2C-bus address are valid. The LSB in
ALLCALLADR register is a read-only bit (0).
If ALLCALL bit = 0 in MODE1 register, the device does not acknowledge the address
programmed in register ALLCALLADR.
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.12 PWMALL — brightness control for all LEDn outputs
When programmed, the value in this register will be used for PWM duty cycle for all the
LEDn outputs and will be reflected in PWM0 through PWM15 registers.
Table 25.
PWMALL - brightness control for all LEDn outputs register (address 44h)
bit description
Legend: * default value.
Address
Register
Bit
Access
Value
Description
44h
PWMALL
7:0
write only
0000 0000*
duty cycle for all LEDn outputs
Remark: Write to any of the PWM0 to PWM15 registers will overwrite the value in
corresponding PWMn register programmed by PWMALL.
7.3.13 IREFALL register: output current value for all LED outputs
The output current setting for all outputs is held in this register. When this register is
written to or updated, all LED outputs will be set to a current corresponding to this register
value.
Writes to IREF0 to IREF15 will overwrite the output current settings.
Table 26. IREFALL - Output gain control for all LED outputs (address 45h) bit description
Legend: * default value.
Address
Register
Bit
Access
Value
Description
45h
IREFALL
7:0
write only
00h*
Current gain setting for all LED outputs.
7.3.14 LED driver constant current outputs
In LED display applications, PCA9955B provides nearly no current variations from
channel to channel and from device to device. The maximum current skew between
channels is less than 4 % and less than 6 % between devices.
7.3.14.1
Adjusting output current
The PCA9955B scales up the reference current (Iref) set by the external resistor (Rext) to
sink the output current (IO) at each output port. The maximum output current for the
outputs can be set using Rext. In addition, the constant value for current drive at each of
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 and Equation 5 can be used to calculate the minimum and maximum constant
current values that can be programmed for the outputs for a chosen Rext.
900 mV 1
I O _LED_MIN = -------------------  ---  minimum constant current 
4
R ext
(4)
900 mV 255
I O _LED_MAX =  255  I O _LED_MIN  =  -------------------  ---------
 R ext
4 
(5)
900 mV 1
For a given IREFx setting, I O _LED = IREFx  -------------------  --- .
4
R ext
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
002aag288
80
IREFx = 255
IO(LEDn)
(mA)
60
40
20
0
1
2
4
3
5
6
8
7
9
10
Rext (kΩ)
IO(LEDn) (mA) = IREFx  (0.9 / 4) / Rext (k)
maximum IO(LEDn) (mA) = 255  (0.9 / 4) / Rext (k)
Remark: Default IREFx at power-up = 0
Fig 10. Maximum ILED versus Rext
Example 1: If Rext = 1 k, IO_LED_MIN = 225 A, IO_LED_MAX = 57.375 mA (as shown
in Figure 11).
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.
002aah691
60
IO(target)
(mA)
50
57.375
40
30
20
10
0
0
32
64
96
128
160
192
224
255
IREFx[7:0] value
Fig 11. IO(target) versus IREFx value with Rext = 1 k
PCA9955B
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PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Example 2: If Rext = 2 k, IO_LED_MIN = 112.5 A, IO_LED_MAX = 28.687 mA (as
shown in Figure 12).
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.
DDK
,2WDUJHW
P$
,5()[>@YDOXH
Fig 12. IO(target) versus IREFx value with Rext = 2 k
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.15 LED error detection
The PCA9955B is capable of detecting an LED open or a short condition at its open-drain
LED outputs. Users will recognize these faults by reading the status of a pair of error bits
(ERRx) in error flag registers (EFLAGn) for each channel. Both LDRx value in LEDOUTx
registers and IREFx value must be set to ‘00’ for those unused LED output channels. If the
output is selected to be fully on, individual dim, or individual and group dim, that channel
will be tested.
The user can poll the ERROR status bit (bit 6 in MODE2 register) to check if there is a
fault condition in any of the 16 channels. The EFLAGn registers can then be read to
determine which channels are at fault and the type of fault in those channels. The error
status reported by the EFLAGn register is real time information that will get self cleared
once the error is fixed and write ‘1’ to CLRERR bit (bit 4 in MODE2 register).
Remark: When LED outputs programmed with LDRx = 10 or 11 in LEDOUT[3:0]
registers, checks for open and short-circuit will not occur if the PWM value in PWM0 to
PWM15 registers is less than 8 or 255 (100 % duty cycle).
Table 27. EFLAG0 to EFLAG3 - Error flag registers (address 46h to 49h) bit description
Legend: * default value.
Address
Register
Bit
Symbol
Access
Value
Description
46h
EFLAG0
7:6
ERR3
R only
00*
Error status for LED3 output
5:4
ERR2
R only
00*
Error status for LED2 output
3:2
ERR1
R only
00*
Error status for LED1 output
1:0
ERR0
R only
00*
Error status for LED0 output
7:6
ERR7
R only
00*
Error status for LED7 output
5:4
ERR6
R only
00*
Error status for LED6 output
3:2
ERR5
R only
00*
Error status for LED5 output
1:0
ERR4
R only
00*
Error status for LED4 output
7:6
ERR11
R only
00*
Error status for LED11 output
5:4
ERR10
R only
00*
Error status for LED10 output
3:2
ERR9
R only
00*
Error status for LED9 output
1:0
ERR8
R only
00*
Error status for LED8 output
7:6
ERR15
R only
00*
Error status for LED15 output
5:4
ERR14
R only
00*
Error status for LED14 output
3:2
ERR13
R only
00*
Error status for LED13 output
1:0
ERR12
R only
00*
Error status for LED12 output
47h
EFLAG1
48h
EFLAG2
49h
Table 28.
EFLAG3
ERRx bit description
LED error detection
status
PCA9955B
Product data sheet
ERRx
Description
Bit 1
Bit 0
No error
0
0
In normal operation and no error
Short-circuit
0
1
Detected LED short-circuit condition
Open-circuit
1
0
Detected LED open-circuit condition
DNE (Do Not Exist)
1
1
This condition does not exist
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PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.3.15.1
Open-circuit detection principle
The PCA9955B LED open-circuit detection compares the effective current level IO with the
open load detection threshold current Ith(det). If IO is below the threshold Ith(det), the
PCA9955B detects an open load condition. This error status can be read out as an
error flag through the EFLAGn registers. For open-circuit error detection of an output
channel, that channel must be ON.
Table 29.
Open-circuit detection
State of
output port
Condition of
output current
Error status code
Description
OFF
IO = 0 mA
ON
[1]
7.3.15.2
0
detection not possible
IO <
Ith(det)[1]
1
open-circuit
IO 
Ith(det)[1]
this channel open error
status bit is 0
normal
Ith(det) = 0.5  IO(target) (typical). This threshold may be different for each I/O and only depends on IREFx and
Rext.
Short-circuit detection principle
The LED short-circuit detection compares the effective output voltage level (VO) with the
shorted-load detection threshold voltages Vth(trig). If VO is above the Vth(trig) threshold, the
PCA9955B detects a shorted-load condition. If VO is below the Vth(trig) threshold, no error
is detected and error bit is set to ‘0’. This error status can be read out as an error flag
through the EFLAGn registers. For short-circuit error detection of an output channel, that
channel must be ON.
Table 30.
Short-circuit detection
State of
output port
Condition of
output voltage
Error status code
Description
OFF
-
0
detection not possible
ON
VO 
1
short-circuit
this channel short error
status bit is 0
normal
Vth(trig)[1]
VO < Vth(trig)
[1]
[1]
Vth  2.85 V.
Remark: The error status distinguishes between an LED short condition and an LED
open condition. Upon detecting an LED short or open, the corresponding LED outputs
should be turned OFF to prevent heat dissipation for a short in the chip. Although an open
event will not be harmful, the outputs should be turned OFF for both occasions to repair
the LED string.
7.3.16 Overtemperature protection
If the PCA9955B chip temperature exceeds its limit (Tth(otp) rising, see Table 33), all output
channels will be disabled until the temperature drops below its limit minus a small
hysteresis (Tth(otp) hysteresis, see Table 33). When an overtemperature situation is
encountered, the OVERTEMP flag (bit 7) is set in the MODE2 register. Once the die
temperature reduces below the Tth(otp) rising  Tth(otp) hysteresis, the chip will return to the
same condition it was prior to the overtemperature event and the OVERTEMP flag will be
cleared.
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.4 Active LOW output enable input
The active LOW output enable (OE) pin on PCA9955B allows to enable or disable all the
LED outputs at the same time.
• When a LOW level is applied to OE pin, all the LED outputs are enabled.
• When a HIGH level is applied to OE pin, all the LED outputs are high-impedance.
The OE pin can be used as a synchronization signal to switch on/off several PCA9955B
devices at the same time when LED drive output state is set fully ON (LDRx = 01 in
LEDOUTx register) in these devices. This requires an external clock reference that
provides blinking period and the duty cycle.
The OE pin can also be used as an external dimming control signal. The frequency of the
external clock must be high enough not to be seen by the human eye, and the duty cycle
value determines the brightness of the LEDs.
Remark: Do not use OE as an external blinking control signal when internal global
blinking is selected (DMBLNK = 1, MODE2 register) since it will result in an undefined
blinking pattern. Do not use OE as an external dimming control signal when internal global
dimming is selected (DMBLNK = 0, MODE2 register) since it will result in an undefined
dimming pattern.
7.5 Power-on reset
When power is applied to VDD, an internal power-on reset holds the PCA9955B in a reset
condition until VDD has reached VPOR. At this point, the reset condition is released and the
PCA9955B registers and I2C-bus state machine are initialized to their default states (all
zeroes) causing all the channels to be deselected. Thereafter, VDD must be pulled lower
than 1 V and stay LOW for longer than 20 s. The device will reset itself, and allow 2 ms
for the device to fully wake up.
7.6 Hardware reset recovery
When a reset of PCA9955B is activated using an active LOW input on the RESET pin, a
reset pulse width of 2.5 s minimum is required. The maximum wait time after RESET pin
is released is 1.5 ms.
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.7 Software reset
The Software Reset Call (SWRST Call) allows all the devices in the I2C-bus to be reset to
the power-up state value through a specific formatted I2C-bus command. To be performed
correctly, it implies that the I2C-bus is functional and that there is no device hanging the
bus.
The maximum wait time after software reset is 1 ms.
The SWRST Call function is defined as the following:
1. A START command is sent by the I2C-bus master.
2. The reserved General Call address ‘0000 000’ with the R/W bit set to ‘0’ (write) is sent
by the I2C-bus master.
3. The PCA9955B device(s) acknowledge(s) after seeing the General Call address
‘0000 0000’ (00h) only. If the R/W bit is set to ‘1’ (read), no acknowledge is returned to
the I2C-bus master.
4. Once the General Call address has been sent and acknowledged, the master sends
1 byte with 1 specific value (SWRST data byte 1):
a. Byte 1 = 06h: the PCA9955B acknowledges this value only. If byte 1 is not equal to
06h, the PCA9955B does not acknowledge it.
If more than 1 byte of data is sent, the PCA9955B does not acknowledge any more.
5. Once the correct byte (SWRST data byte 1) has been sent and correctly
acknowledged, the master sends a STOP condition to end the SWRST function: the
PCA9955B then resets to the default value (power-up value) and is ready to be
addressed again within the specified bus free time (tBUF).
General Call address
S
0
0
0
0
START condition
0
0
0
SWRST data byte 1
0
A
0
0
0
acknowledge
from slave
0
0
1
1
0
A
P
acknowledge
from slave
STOP
condition
002aac900
Fig 13. SWRST Call
The I2C-bus master must interpret a non-acknowledge from the PCA9955B (at any time)
as a ‘SWRST Call Abort’. The PCA9955B does not initiate a reset of its registers. This
happens only when the format of the SWRST Call sequence is not correct.
PCA9955B
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PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
7.8 Individual brightness control with group dimming/blinking
A 31.25 kHz fixed frequency signal with programmable duty cycle (8 bits, 256 steps) is
used to control individually the brightness for each LED.
On top of this signal, one of the following signals can be superimposed (this signal can be
applied to the 16 LED outputs LED0 to LED15).
• A lower 122 Hz fixed frequency signal with programmable duty cycle (8 bits,
256 steps) is used to provide a global brightness control.
• A programmable frequency signal from 15 Hz to every 16.8 seconds (8 bits,
256 steps) with programmable duty cycle (8 bits, 256 steps) is used to provide a
global blinking control.
1
2
3
4
5
6
7
8
9 10 11 12
251
252
253
254
255
256
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
9 10 11
Brightness Control signal (LEDn)
N × 125 ns
with N = (0 to 255)
(PWMx Register)
M × 256 × 125 ns
with M = (0 to 255)
(GRPPWM Register)
256 × 125 ns = 32 μs
(31.25 kHz)
Group Dimming signal
256 × 256 × 125 ns = 8.19 ms (122 Hz)
1
2
3
4
5
6
7
8
resulting Brightness + Group Dimming signal
002aaf935
Minimum pulse width for LEDn Brightness Control is 125 ns
Minimum pulse width for Group Dimming is 32 s
When M = 1 (GRPPWM register value), the resulting LEDn Brightness Control + Group Dimming signal will have 1 pulse of the
LED Brightness Control signal (pulse width = N  125 ns, with ‘N’ defined in PWMx register)
This resulting Brightness + Group Dimming signal above shows a resulting Control signal with M = 8
Fig 14. Brightness + Group Dimming signals
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
8. Characteristics of the I2C-bus
The I2C-bus is for 2-way, 2-line communication between different ICs or modules. The two
lines are a serial data line (SDA) and a serial clock line (SCL). Both lines must be
connected to a positive supply via a pull-up resistor when connected to the output stages
of a device. Data transfer may be initiated only when the bus is not busy.
8.1 Bit transfer
One data bit is transferred during each clock pulse. The data on the SDA line must remain
stable during the HIGH period of the clock pulse as changes in the data line at this time
will be interpreted as control signals (see Figure 15).
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Fig 15. Bit transfer
8.1.1 START and STOP conditions
Both data and clock lines remain HIGH when the bus is not busy. A HIGH-to-LOW
transition of the data line while the clock is HIGH is defined as the START condition (S). A
LOW-to-HIGH transition of the data line while the clock is HIGH is defined as the STOP
condition (P) (see Figure 16).
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3
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Fig 16. Definition of START and STOP conditions
8.2 System configuration
A device generating a message is a ‘transmitter’; a device receiving is the ‘receiver’. The
device that controls the message is the ‘master’ and the devices which are controlled by
the master are the ‘slaves’ (see Figure 17).
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
SDA
SCL
MASTER
TRANSMITTER/
RECEIVER
SLAVE
RECEIVER
SLAVE
TRANSMITTER/
RECEIVER
MASTER
TRANSMITTER
MASTER
TRANSMITTER/
RECEIVER
I2C-BUS
MULTIPLEXER
SLAVE
002aaa966
Fig 17. System configuration
8.3 Acknowledge
The number of data bytes transferred between the START and the STOP conditions from
transmitter to receiver is not limited. Each byte of eight bits is followed by one
acknowledge bit. The acknowledge bit is a HIGH level put on the bus by the transmitter,
whereas the master generates an extra acknowledge related clock pulse.
A slave receiver which is addressed must generate an acknowledge after the reception of
each byte. Also a master must generate an acknowledge after the reception of each byte
that has been clocked out of the slave transmitter. The device that acknowledges has to
pull down the SDA line during the acknowledge clock pulse, so that the SDA line is stable
LOW during the HIGH period of the acknowledge related clock pulse; set-up time and hold
time must be taken into account.
A master receiver must signal an end of data to the transmitter by not generating an
acknowledge on the last byte that has been clocked out of the slave. In this event, the
transmitter must leave the data line HIGH to enable the master to generate a STOP
condition.
data output
by transmitter
not acknowledge
data output
by receiver
acknowledge
SCL from master
1
2
S
START
condition
8
9
clock pulse for
acknowledgement
002aaa987
Fig 18. Acknowledgement on the I2C-bus
PCA9955B
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
9. Bus transactions
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(1) See Table 7 for register definition
Fig 19. Write to a specific register
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(1) AI1, AI0 = 00. See Table 6 for Auto-Increment options
Remark: Care should be taken to load the appropriate value here in the AI1 and AI0 bits of the MODE1 register for
programming the part with the required Auto-Increment options
Fig 20. Write to all registers using the Auto-Increment feature
PCA9955B
Product data sheet
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NXP Semiconductors
PCA9955B
Product data sheet
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Fig 21. Multiple writes to Individual Brightness registers only using the Auto-Increment feature
PCA9955B
43 of 62
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This example assumes that AIF + AI[1:0] = 101b
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Rev. 2 — 20 November 2015
All information provided in this document is subject to legal disclaimers.
67$57FRQGLWLRQ
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
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This example assumes that the MODE1[5] = 0 and MODE1[6] = 0
Fig 22. Read all registers using the Auto-Increment feature
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Remark: A read operation can be done without doing a write operation before it. In this case, the data sent out is from the
register pointed to by the control register (written to during the last write operation) with the Auto-Increment options in the
MODE1 register (written to during the last write operation)
Fig 23. Read of registers
PCA9955B
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Rev. 2 — 20 November 2015
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44 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
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(1) In this example, several PCA9955Bs are used and the same sequence (A) (above) is sent to each of them
(2) ALLCALL bit in MODE1 register is previously set to 1 for this example
(3) OCH bit in MODE2 register is previously set to 1 for this example
Fig 24. LED All Call I2C-bus address programming and LED All Call sequence example
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NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
10. Application design-in information
VDD = 3.3 V or 5.0 V
1.6 kΩ
1.6 kΩ
10 kΩ(1)
10 kΩ(3)
up to 20 V
I2C-BUS/SMBus
MASTER
SDA
SDA
SCL
SCL
OE
OE
VDD
RESET
LED0
LED1
LED2
RESET
LED3
LED4
PCA9955B
LED5
LED6
LED7
REXT
LED8
ISET
LED9
LED10
AD0(2)
LED11
AD1
AD2
LED12
LED13
LED14
VSS
LED15
VSS
C
10 μF
aaa-016964
(1) OE requires pull-up resistor if control signal from the master is open-drain
(2) I2C-bus address = 1101001 when AD0, AD2 tied to VDD and AD1 tied to VSS (see Table 5)
(3) RESET requires a pull-up resistor of <100 k if not used or connected to open-drain output
Fig 25. Typical application
10.1 Thermal considerations
Since the PCA9955B device integrates 16 linear current sources, thermal considerations
should be taken into account to prevent overheating, which can cause the device to go
into thermal shutdown.
Perhaps the major contributor for device’s overheating is the LED forward voltage
mismatch. This is because it can cause significant voltage differences between the LED
strings of the same type (for example, 2 V to 3 V), which ultimately translates into higher
power dissipation in the device. The voltage drop across the LED channels of the device
is given by the difference between the supply voltage and the LED forward voltage of each
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Product data sheet
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Rev. 2 — 20 November 2015
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NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
LED string. Reducing this to a minimum (for example, 0.8 V) helps to keep the power
dissipation down. Therefore LEDs binning is recommended to minimize LED voltage
forward variation and reduce power dissipation in the device.
In order to ensure that the device will not go into thermal shutdown when operating under
certain application conditions, its junction temperature (Tj) should be calculated to ensure
that is below the overtemperature threshold limit (130 C). The Tj of the device depends
on the ambient temperature (Tamb), device’s total power dissipation (Ptot), and thermal
resistance.
The device junction temperature can be calculated by using the following equation:
T j = T amb + R th  j-a   P tot
(6)
where:
Tj = junction temperature
Tamb = ambient temperature
Rth(j-a) = junction to ambient thermal resistance
Ptot = (device) total power dissipation
An example of this calculation is show below:
Conditions:
Tamb = 50 C
Rth(j-a) = 39 C/W (per JEDEC 51 standard for multilayer PCB)
ILED = 30 mA / channel
IDD(max) = 20 mA
VDD = 5 V
LEDs per channel = 5 LEDs / channel
LED VF(typ) = 3 V per LED (15 V total for 5 LEDs in series)
LED VF mismatch = 0.2 V per LED (1 V total for 5 LEDs in series)
Vreg(drv) = 0.8 V (This will be present only in the LED string with the highest LED forward
voltage.)
Vsup = LED VF(typ) + LED VF mismatch + Vreg(drv) = 15 V + 1 V + 0.8 V = 16.8 V
Ptot calculation:
Ptot = IC_power + LED drivers_power;
IC_power = (IDD  VDD) + (SDA_VOL  IOL)
IC_power = (0.02 A  5 V) + (0.4 V  0.03 A) = 0.112 W
LED drivers_power = [(16  1)  (ILED)  (LED VF mismatch + Vreg(drv))] +
(ILED  Vreg(drv))
LED drivers_power = [15  0.03 A  (1 V + 0.8 V)] + (0.03 A  0.8 V) = 0.834 W
Ptot = 0.112 W + 0.834 W = 0.946 W
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NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Tj calculation:
Tj = Tamb + Rth(j-a)  Ptot
Tj = 50 C + (39 C/W  0.946 W) = 86.894 C
This confirms that the junction temperature is below the minimum overtemperature
threshold of 130 C, which ensures the device will not go into thermal shutdown under
these conditions.
It is important to mention that the value of the thermal resistance junction-to-ambient
(Rth(j-a)) strongly depends in the PCB design. Therefore, the thermal pad of the device
should be attached to a big enough PCB copper area to ensure proper thermal dissipation
(similar to JEDEC 51 standard). Several thermal vias in the PCB thermal pad should be
used as well to increase the effectiveness of the heat dissipation (for example, 15 thermal
vias). The thermal vias should be distributed evenly in the PCB thermal pad.
Finally, it is important to point out that this calculation should be taken as a reference only
and therefore evaluations should still be performed under the application environment and
conditions to confirm proper system operation.
11. Limiting values
Table 31. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol
Parameter
Min
Max
Unit
VDD
supply voltage
Conditions
0.5
+6.0
V
VI/O
voltage on an input/output pin
VSS  0.5
5.5
V
Vdrv(LED)
LED driver voltage
VSS  0.5
20
V
IO(LEDn)
output current on pin LEDn
-
65
mA
ISS
ground supply current
-
1.0
A
Ptot
total power dissipation
Tamb = 25 C
-
2.56
W
Tamb = 85 C
-
1.03
W
65
+150
C
40
+85
C
40
+125
C
Tstg
storage temperature
Tamb
ambient temperature
Tj
junction temperature
operating
12. Thermal characteristics
Table 32.
Symbol
Rth(j-a)
[1]
Thermal characteristics
Parameter
Conditions
thermal resistance from junction to ambient
HTSSOP28
[1]
Typ
Unit
39
C/W
Per JEDEC 51 standard for multilayer PCB and Wind Speed (m/s) = 0.
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Product data sheet
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Rev. 2 — 20 November 2015
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NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
13. Static characteristics
Table 33. Static characteristics
VDD = 3 V to 5.5 V; VSS = 0 V; Tamb = 40 C to +85 C; unless otherwise specified.
Symbol
Parameter
Min
Typ[1]
Max
Unit
3
-
5.5
V
Rext = 2 k; LED[15:0] = off;
IREFx = 00h
-
11
12
mA
Rext = 1 k; LED[15:0] = off;
IREFx = 00h
-
13
14
mA
Rext = 2 k; LED[15:0] = on;
IREFx = FFh
-
15
19
mA
Rext = 1 k; LED[15:0] = on;
IREFx = FFh
-
17
21
mA
VDD = 3.3 V
-
170
600
A
VDD = 5.5 V
-
170
700
A
-
2
-
V
-
1
-
V
-
+0.3VDD V
Conditions
Supply
VDD
supply voltage
IDD
supply current
Istb
VPOR
VPDR
standby current
power-on reset voltage
power-down reset voltage
on pin VDD; operating mode;
fSCL = 1 MHz
on pin VDD; no load; fSCL = 0 Hz;
MODE1[4] = 1; VI = VDD
no load; VI = VDD or VSS
no load; VI = VDD or VSS
[2][5]
Input SCL; input/output SDA
VIL
LOW-level input voltage
0.5
VIH
HIGH-level input voltage
0.7VDD -
5.5
V
IOL
LOW-level output current
VOL = 0.4 V; VDD = 3 V
20
-
-
mA
VOL = 0.4 V; VDD = 5 V
30
-
-
mA
IL
leakage current
VI = VDD or VSS
1
-
+1
A
Ci
input capacitance
VI = VSS
-
6
10
pF
Current controlled outputs (LED[15:0])
IO(LEDn)
output current on pin LEDn
VO = 0.8 V; IREFx = 80h; Rext = 1 k
25
-
30
mA
[5]
50
-
60
mA
between bits (different ICs, same
channel)
[3]
-
-
6
%
between bits (2 channels, same IC)
[4]
VO = 0.8 V; IREFx = FFh; Rext = 1 k
IO
output current variation
VDD = 3.0 V; Tamb = 25 C;
VO = 0.8 V; IREFx = 80h; Rext = 1 k;
guaranteed by design
-
-
4
%
Vreg(drv)
driver regulation voltage
minimum regulation voltage;
IREFx = FFh; Rext = 1 k
0.8
1
20
V
IL(off)
off-state leakage current
VO = 20 V
-
-
1
A
Vtrip
trip voltage
short LED protection; Error flag will
trip during verification test if
VO  Vtrip; Rext = 1 k
2.7
2.85
-
V
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Rev. 2 — 20 November 2015
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NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Table 33. Static characteristics …continued
VDD = 3 V to 5.5 V; VSS = 0 V; Tamb = 40 C to +85 C; unless otherwise specified.
Symbol
Parameter
Conditions
Min
Typ[1]
Max
-
+0.3VDD V
Unit
OE input, RESET input
VIL
LOW-level input voltage
0.5
VIH
HIGH-level input voltage
0.7VDD -
5.5
V
ILI
input leakage current
1
-
+1
A
-
3.7
5
pF
0.5
-
5.5
V
1
-
+1
A
[5]
-
3.7
5
pF
rising
[5]
130
-
150
C
hysteresis
[5]
15
-
30
C
[5]
input capacitance
Ci
Address inputs AD2, AD1, AD0
VI
input voltage
ILI
input leakage current
voltage on an input pin
input capacitance
Ci
Overtemperature protection
Tth(otp)
[1]
overtemperature protection
threshold temperature
Typical limits at VDD = 3.3 V, Tamb = 25 C.
[2]
VDD must be lowered to 1 V in order to reset part.
[3]
Part-to-part mismatch is calculated:
I O  LED0  + I O  LED1  +  + I O  LED14  + I O  LED15 
  --------------------------------------------------------------------------------------------------------------------------- – ideal output current 


16
% =  ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------  100
ideal output current




where ‘ideal output current’ = 28.68 mA (Rext = 1 k, IREFx = 80h).
[4]
Channel-to-channel mismatch is calculated:


I O  LEDn   where n = 0 to 15 


% =  --------------------------------------------------------------------------------------------------------------------------------- – 1  100
+
I
+

+
I
+
I
I
  O  LED0  O  LED1 

O  LED14 
O  LED15 
  --------------------------------------------------------------------------------------------------------------------------

16
[5]
Value not tested in production, but guaranteed by design and characterization.
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NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
14. Dynamic characteristics
Table 34.
Symbol
Dynamic characteristics
Parameter
Conditions
Standard-mode
I2C-bus
Min
Max
Fast-mode
I2C-bus
Fast-mode
Plus I2C-bus
Min
Max
Min
Max
Unit
fSCL
SCL clock frequency
0
100
0
400
0
1000
tBUF
bus free time between a
STOP and START condition
4.7
-
1.3
-
0.5
-
kHz
s
tHD;STA
hold time (repeated) START
condition
4.0
-
0.6
-
0.26
-
s
tSU;STA
set-up time for a repeated
START condition
4.7
-
0.6
-
0.26
-
s
tSU;STO
set-up time for STOP
condition
4.0
-
0.6
-
0.26
-
s
tHD;DAT
data hold time
0
-
0
-
0
-
ns
data valid acknowledge time
[1]
0.3
3.45
0.1
0.9
0.05
0.45
s
tVD;DAT
data valid time
[2]
0.3
3.45
0.1
0.9
0.05
0.45
s
tSU;DAT
data set-up time
250
-
100
-
50
-
ns
tLOW
LOW period of the SCL clock
4.7
-
1.3
-
0.5
-
s
tHIGH
HIGH period of the SCL clock
4.0
-
0.6
tVD;ACK
tf
fall time of both SDA and
SCL signals
tr
rise time of both SDA and
SCL signals
tSP
pulse width of spikes that
must be suppressed by the
input filter
tw(rst)
reset pulse width
[1]
[3][4]
[6]
-
0.26
-
s
[5]
300
-
120
ns
-
300
20 + 0.1Cb
-
1000
20 + 0.1Cb[5]
300
-
120
ns
-
50
-
50
-
50
ns
2.5
-
2.5
-
2.5
-
s
tVD;ACK = time for Acknowledgement signal from SCL LOW to SDA (out) LOW.
[2]
tVD;DAT = minimum time for SDA data out to be valid following SCL LOW.
[3]
A master device must internally provide a hold time of at least 300 ns for the SDA signal (refer to the VIL of the SCL signal) in order to
bridge the undefined region of SCL’s falling edge.
[4]
The maximum tf for the SDA and SCL bus lines is specified at 300 ns. The maximum fall time (tf) for the SDA output stage is specified at
250 ns. This allows series protection resistors to be connected between the SDA and the SCL pins and the SDA/SCL bus lines without
exceeding the maximum specified tf.
[5]
Cb = total capacitance of one bus line in pF.
[6]
Input filters on the SDA and SCL inputs suppress noise spikes less than 50 ns.
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16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
0.7 × VDD
SDA
0.3 × VDD
tr
tBUF
tf
tHD;STA
tSP
tLOW
0.7 × VDD
SCL
0.3 × VDD
tHD;STA
P
tSU;STA
tHD;DAT
S
tHIGH
tSU;DAT
tSU;STO
Sr
P
002aaa986
Fig 26. Definition of timing
protocol
START
condition
(S)
bit 7
MSB
(A7)
tSU;STA
tLOW
bit 6
(A6)
tHIGH
bit 1
(D1)
bit 0
(D0)
STOP
condition
(P)
acknowledge
(A)
1 / fSCL
0.7 × VDD
SCL
0.3 × VDD
tBUF
tf
tr
0.7 × VDD
SDA
0.3 × VDD
tSU;DAT
tHD;STA
tVD;ACK
tVD;DAT
tHD;DAT
tSU;STO
002aab285
Rise and fall times refer to VIL and VIH
Fig 27. I2C-bus timing diagram
15. Test information
9''
38/6(
*(1(5$725
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5/
92
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RSHQ
966
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57
&/
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DDJ
RL = Load resistor for LEDn
CL = Load capacitance includes jig and probe capacitance
RT = Termination resistance should be equal to the output impedance Zo of the pulse generators
Fig 28. Test circuitry for switching times
PCA9955B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
52 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
16. Package outline
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Fig 29. Package outline SOT1172-3 (HTSSOP28)
PCA9955B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
53 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
17. Handling information
All input and output pins are protected against ElectroStatic Discharge (ESD) under
normal handling. When handling ensure that the appropriate precautions are taken as
described in JESD625-A or equivalent standards.
18. Soldering of SMD packages
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering ICs can be found in Application Note AN10365 “Surface mount reflow
soldering description”.
18.1 Introduction to soldering
Soldering is one of the most common methods through which packages are attached to
Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both
the mechanical and the electrical connection. There is no single soldering method that is
ideal for all IC packages. Wave soldering is often preferred when through-hole and
Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not
suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high
densities that come with increased miniaturization.
18.2 Wave and reflow soldering
Wave soldering is a joining technology in which the joints are made by solder coming from
a standing wave of liquid solder. The wave soldering process is suitable for the following:
• Through-hole components
• Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless
packages which have solder lands underneath the body, cannot be wave soldered. Also,
leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,
due to an increased probability of bridging.
The reflow soldering process involves applying solder paste to a board, followed by
component placement and exposure to a temperature profile. Leaded packages,
packages with solder balls, and leadless packages are all reflow solderable.
Key characteristics in both wave and reflow soldering are:
•
•
•
•
•
•
Board specifications, including the board finish, solder masks and vias
Package footprints, including solder thieves and orientation
The moisture sensitivity level of the packages
Package placement
Inspection and repair
Lead-free soldering versus SnPb soldering
18.3 Wave soldering
Key characteristics in wave soldering are:
PCA9955B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
54 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
• Process issues, such as application of adhesive and flux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
• Solder bath specifications, including temperature and impurities
18.4 Reflow soldering
Key characteristics in reflow soldering are:
• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see Figure 30) than a SnPb process, thus
reducing the process window
• Solder paste printing issues including smearing, release, and adjusting the process
window for a mix of large and small components on one board
• Reflow temperature profile; this profile includes preheat, reflow (in which the board is
heated to the peak temperature) and cooling down. It is imperative that the peak
temperature is high enough for the solder to make reliable solder joints (a solder paste
characteristic). In addition, the peak temperature must be low enough that the
packages and/or boards are not damaged. The peak temperature of the package
depends on package thickness and volume and is classified in accordance with
Table 35 and 36
Table 35.
SnPb eutectic process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
 350
< 2.5
235
220
 2.5
220
220
Table 36.
Lead-free process (from J-STD-020D)
Package thickness (mm)
Package reflow temperature (C)
Volume (mm3)
< 350
350 to 2000
> 2000
< 1.6
260
260
260
1.6 to 2.5
260
250
245
> 2.5
250
245
245
Moisture sensitivity precautions, as indicated on the packing, must be respected at all
times.
Studies have shown that small packages reach higher temperatures during reflow
soldering, see Figure 30.
PCA9955B
Product data sheet
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Rev. 2 — 20 November 2015
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55 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
temperature
maximum peak temperature
= MSL limit, damage level
minimum peak temperature
= minimum soldering temperature
peak
temperature
time
001aac844
MSL: Moisture Sensitivity Level
Fig 30. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description”.
PCA9955B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
56 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
19. Soldering: PCB footprints
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Fig 31. PCB footprint for SOT1172-3 (HTSSOP28); reflow soldering
PCA9955B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
57 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
20. Abbreviations
Table 37.
Abbreviations
Acronym
Description
ACK
Acknowledge
CDM
Charged-Device Model
DAC
Digital-to-Analog Converter
DUT
Device Under Test
ESD
ElectroStatic Discharge
FET
Field-Effect Transistor
HBM
Human Body Model
I2C-bus
Inter-Integrated Circuit bus
LED
Light Emitting Diode
LSB
Least Significant Bit
MCU
MicroController Unit
MSB
Most Significant Bit
NMOS
Negative-channel Metal-Oxide Semiconductor
PCB
Printed-Circuit Board
PMOS
Positive-channel Metal-Oxide Semiconductor
PWM
Pulse Width Modulation
RGB
Red/Green/Blue
RGBA
Red/Green/Blue/Amber
SMBus
System Management Bus
21. Revision history
Table 38.
Revision history
Document ID
Release date
Data sheet status
Change notice
Supersedes
PCA9955B v.2
20151120
Product data sheet
-
PCA9955B v.1
Modifications:
PCA9955B v.1
PCA9955B
Product data sheet
•
•
•
Corrected Figure 1 “Block diagram of PCA9955B”
Table 3 “Pin description”: Corrected description for RESET pin
Corrected Figure 25 “Typical application”; added Figure note 3
20150622
Product data sheet
-
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
-
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PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
22. Legal information
22.1 Data sheet status
Document status[1][2]
Product status[3]
Definition
Objective [short] data sheet
Development
This document contains data from the objective specification for product development.
Preliminary [short] data sheet
Qualification
This document contains data from the preliminary specification.
Product [short] data sheet
Production
This document contains the product specification.
[1]
Please consult the most recently issued document before initiating or completing a design.
[2]
The term ‘short data sheet’ is explained in section “Definitions”.
[3]
The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
22.2 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
Product specification — The information and data provided in a Product
data sheet shall define the specification of the product as agreed between
NXP Semiconductors and its customer, unless NXP Semiconductors and
customer have explicitly agreed otherwise in writing. In no event however,
shall an agreement be valid in which the NXP Semiconductors product is
deemed to offer functions and qualities beyond those described in the
Product data sheet.
22.3 Disclaimers
Limited warranty and liability — Information in this document is believed to
be accurate and reliable. However, NXP Semiconductors does not give any
representations or warranties, expressed or implied, as to the accuracy or
completeness of such information and shall have no liability for the
consequences of use of such information. NXP Semiconductors takes no
responsibility for the content in this document if provided by an information
source outside of NXP Semiconductors.
In no event shall NXP Semiconductors be liable for any indirect, incidental,
punitive, special or consequential damages (including - without limitation - lost
profits, lost savings, business interruption, costs related to the removal or
replacement of any products or rework charges) whether or not such
damages are based on tort (including negligence), warranty, breach of
contract or any other legal theory.
Notwithstanding any damages that customer might incur for any reason
whatsoever, NXP Semiconductors’ aggregate and cumulative liability towards
customer for the products described herein shall be limited in accordance
with the Terms and conditions of commercial sale of NXP Semiconductors.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
PCA9955B
Product data sheet
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in life support, life-critical or
safety-critical systems or equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors and its suppliers accept no liability for
inclusion and/or use of NXP Semiconductors products in such equipment or
applications and therefore such inclusion and/or use is at the customer’s own
risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Customers are responsible for the design and operation of their applications
and products using NXP Semiconductors products, and NXP Semiconductors
accepts no liability for any assistance with applications or customer product
design. It is customer’s sole responsibility to determine whether the NXP
Semiconductors product is suitable and fit for the customer’s applications and
products planned, as well as for the planned application and use of
customer’s third party customer(s). Customers should provide appropriate
design and operating safeguards to minimize the risks associated with their
applications and products.
NXP Semiconductors does not accept any liability related to any default,
damage, costs or problem which is based on any weakness or default in the
customer’s applications or products, or the application or use by customer’s
third party customer(s). Customer is responsible for doing all necessary
testing for the customer’s applications and products using NXP
Semiconductors products in order to avoid a default of the applications and
the products or of the application or use by customer’s third party
customer(s). NXP does not accept any liability in this respect.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) will cause permanent
damage to the device. Limiting values are stress ratings only and (proper)
operation of the device at these or any other conditions above those given in
the Recommended operating conditions section (if present) or the
Characteristics sections of this document is not warranted. Constant or
repeated exposure to limiting values will permanently and irreversibly affect
the quality and reliability of the device.
Terms and conditions of commercial sale — NXP Semiconductors
products are sold subject to the general terms and conditions of commercial
sale, as published at http://www.nxp.com/profile/terms, unless otherwise
agreed in a valid written individual agreement. In case an individual
agreement is concluded only the terms and conditions of the respective
agreement shall apply. NXP Semiconductors hereby expressly objects to
applying the customer’s general terms and conditions with regard to the
purchase of NXP Semiconductors products by customer.
No offer to sell or license — Nothing in this document may be interpreted or
construed as an offer to sell products that is open for acceptance or the grant,
conveyance or implication of any license under any copyrights, patents or
other industrial or intellectual property rights.
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
59 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
Export control — This document as well as the item(s) described herein
may be subject to export control regulations. Export might require a prior
authorization from competent authorities.
Non-automotive qualified products — Unless this data sheet expressly
states that this specific NXP Semiconductors product is automotive qualified,
the product is not suitable for automotive use. It is neither qualified nor tested
in accordance with automotive testing or application requirements. NXP
Semiconductors accepts no liability for inclusion and/or use of
non-automotive qualified products in automotive equipment or applications.
In the event that customer uses the product for design-in and use in
automotive applications to automotive specifications and standards, customer
(a) shall use the product without NXP Semiconductors’ warranty of the
product for such automotive applications, use and specifications, and (b)
whenever customer uses the product for automotive applications beyond
NXP Semiconductors’ specifications such use shall be solely at customer’s
own risk, and (c) customer fully indemnifies NXP Semiconductors for any
liability, damages or failed product claims resulting from customer design and
use of the product for automotive applications beyond NXP Semiconductors’
standard warranty and NXP Semiconductors’ product specifications.
Translations — A non-English (translated) version of a document is for
reference only. The English version shall prevail in case of any discrepancy
between the translated and English versions.
22.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
I2C-bus — logo is a trademark of NXP Semiconductors N.V.
23. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
PCA9955B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
60 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
24. Contents
1
2
3
4
4.1
5
6
6.1
6.2
7
7.1
7.1.1
7.1.2
7.1.3
7.2
7.3
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.3.6
7.3.7
7.3.8
7.3.8.1
7.3.8.2
7.3.8.3
7.3.8.4
7.3.8.5
General description . . . . . . . . . . . . . . . . . . . . . . 1
Features and benefits . . . . . . . . . . . . . . . . . . . . 2
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Ordering information . . . . . . . . . . . . . . . . . . . . . 4
Ordering options . . . . . . . . . . . . . . . . . . . . . . . . 4
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Pinning information . . . . . . . . . . . . . . . . . . . . . . 6
Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 7
Functional description . . . . . . . . . . . . . . . . . . . 8
Device addresses . . . . . . . . . . . . . . . . . . . . . . . 8
Regular I2C-bus slave address. . . . . . . . . . . . . 8
LED All Call I2C-bus address . . . . . . . . . . . . . 12
LED Sub Call I2C-bus addresses . . . . . . . . . . 12
Control register . . . . . . . . . . . . . . . . . . . . . . . . 13
Register definitions . . . . . . . . . . . . . . . . . . . . . 14
MODE1 — Mode register 1 . . . . . . . . . . . . . . 17
MODE2 — Mode register 2 . . . . . . . . . . . . . . 18
LEDOUT0 to LEDOUT3, LED driver output
state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
GRPPWM, group duty cycle control . . . . . . . . 19
GRPFREQ, group frequency . . . . . . . . . . . . . 20
PWM0 to PWM15, individual brightness
control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
IREF0 to IREF15, LED output current value
registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Gradation control . . . . . . . . . . . . . . . . . . . . . . 22
RAMP_RATE_GRP0 to RAMP_RATE_GRP3,
ramp rate control registers . . . . . . . . . . . . . . . 23
STEP_TIME_GRP0 to STEP_TIME_GRP3, step
time control registers . . . . . . . . . . . . . . . . . . . 23
HOLD_CNTL_GRP0 to HOLD_CNTL_GRP3,
hold ON and OFF control registers. . . . . . . . . 24
IREF_GRP0 to IREF_GRP3, output gain
control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
GRAD_MODE_SEL0 to GRAD_MODE_SEL1,
Gradation mode select registers. . . . . . . . . . . 25
7.3.8.6
GRAD_GRP_SEL0 to GRAD_GRP_SEL3,
Gradation group select registers . . . . . . . . . . 25
7.3.8.7
GRAD_CNTL, Gradation control register. . . . 26
7.3.8.8
Ramp control — equation and calculation
example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.3.9
OFFSET — LEDn output delay offset register 30
7.3.10
LED Sub Call I2C-bus addresses for
PCA9955B . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7.3.11
ALLCALLADR, LED All Call I2C-bus address 31
7.3.12
PWMALL — brightness control for all LEDn
outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
7.3.13
IREFALL register: output current value for all LED
outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
7.3.14
LED driver constant current outputs. . . . . . . . 32
7.3.14.1 Adjusting output current . . . . . . . . . . . . . . . . . 32
7.3.15
LED error detection . . . . . . . . . . . . . . . . . . . . 35
7.3.15.1 Open-circuit detection principle . . . . . . . . . . . 36
7.3.15.2 Short-circuit detection principle . . . . . . . . . . . 36
7.3.16
Overtemperature protection . . . . . . . . . . . . . . 36
7.4
Active LOW output enable input . . . . . . . . . . 37
7.5
Power-on reset. . . . . . . . . . . . . . . . . . . . . . . . 37
7.6
Hardware reset recovery . . . . . . . . . . . . . . . . 37
7.7
Software reset . . . . . . . . . . . . . . . . . . . . . . . . 38
7.8
Individual brightness control with group
dimming/blinking . . . . . . . . . . . . . . . . . . . . . . 39
8
Characteristics of the I2C-bus . . . . . . . . . . . . 40
8.1
Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
8.1.1
START and STOP conditions. . . . . . . . . . . . . 40
8.2
System configuration . . . . . . . . . . . . . . . . . . . 40
8.3
Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . 41
9
Bus transactions . . . . . . . . . . . . . . . . . . . . . . . 42
10
Application design-in information. . . . . . . . . 46
10.1
Thermal considerations . . . . . . . . . . . . . . . . . 46
11
Limiting values . . . . . . . . . . . . . . . . . . . . . . . . 48
12
Thermal characteristics . . . . . . . . . . . . . . . . . 48
13
Static characteristics . . . . . . . . . . . . . . . . . . . 49
14
Dynamic characteristics. . . . . . . . . . . . . . . . . 51
15
Test information . . . . . . . . . . . . . . . . . . . . . . . 52
continued >>
PCA9955B
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 20 November 2015
© NXP Semiconductors N.V. 2015. All rights reserved.
61 of 62
PCA9955B
NXP Semiconductors
16-channel Fm+ I2C-bus 57 mA/20 V constant current LED driver
16
17
18
18.1
18.2
18.3
18.4
19
20
21
22
22.1
22.2
22.3
22.4
23
24
Package outline . . . . . . . . . . . . . . . . . . . . . . . .
Handling information. . . . . . . . . . . . . . . . . . . .
Soldering of SMD packages . . . . . . . . . . . . . .
Introduction to soldering . . . . . . . . . . . . . . . . .
Wave and reflow soldering . . . . . . . . . . . . . . .
Wave soldering . . . . . . . . . . . . . . . . . . . . . . . .
Reflow soldering . . . . . . . . . . . . . . . . . . . . . . .
Soldering: PCB footprints. . . . . . . . . . . . . . . .
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . .
Revision history . . . . . . . . . . . . . . . . . . . . . . . .
Legal information. . . . . . . . . . . . . . . . . . . . . . .
Data sheet status . . . . . . . . . . . . . . . . . . . . . .
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . .
Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . .
Contact information. . . . . . . . . . . . . . . . . . . . .
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
53
54
54
54
54
54
55
57
58
58
59
59
59
59
60
60
61
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP Semiconductors N.V. 2015.
All rights reserved.
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Date of release: 20 November 2015
Document identifier: PCA9955B