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INTEGRATED CIRCUITS
PCA9531
8-bit I2C LED dimmer
Product data
Philips
Semiconductors
2003 Nov 10

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Philips Semiconductors
8-bit I2C LED dimmer
Product data
PCA9531
FEATURES
Eight LED drivers (on, off, flashing at a programmable rate)
Two selectable, fully programmable blink rates (frequency and
duty cycle) between 0.625 and 160 Hz (1.6 and 6.25 milliseconds)
256 brightness steps
Input/outputs not used as LED drivers can be used as regular
GPIOs
Internal oscillator requires no external components
I2C interface logic compatible with SMBus
Internal power-on reset
Noise filter on SCL/SDA inputs
Active low reset input
Eight open drain outputs directly drive LEDs to 25 mA
Edge rate control on outputs
No glitch on power-up
Supports hot insertion
Low stand-by current
Operating power supply voltage range of 2.3 V to 5.5 V
0 to 400 kHz clock frequency
ESD protection exceeds 2000 V HBM per JESD22-A114,
150 V MM per JESD22-A115 and 1000 V CDM per JESD22-C101
Latch-up testing is done to JEDEC Standard JESD78 which
exceeds 100 mA
Package offer: SO16, TSSOP16, HVQFN16
DESCRIPTION
The PCA9531 is an 8-bit I2C & SMBus I/O expander optimized for
dimming LEDs in 256 discrete steps for Red/Green/Blue (RGB)
color mixing and back light applications.
The PCA9531 contains an internal oscillator with two user
programmable blink rates and duty cycles coupled to the output
PWM. The LED brightness is controlled by setting the blink rate high
enough (> 100 Hz) that the blinking can not be seen and then using
the duty cycle to vary the amount of time the LED is on and thus the
average current through the LED.
The initial setup sequence programs the two blink rates/duty cycles
for each individual PWM. From then on, only one command from the
bus master is required to turn individual LEDs ON, OFF, BLINK
RATE 1 or BLINK RATE 2. Based on the programmed frequency
and duty cycle, BLINK RATE 1 and BLINK RATE 2 will cause the
LEDs to appear at a different brightness or blink at periods up to 1.6
second. The open drain outputs directly drive the LEDs with
maximum output sink current of 25 mA per bit and 100 mA per
package.
To blink LEDs at periods greater than 1.6 second the bus master
(MCU, MPU, DSP, chipset, etc.) must send repeated commands to
turn the LED on and off as is currently done when using normal I/O
Expanders like the Philips PCF8574 or PCA9554. Any bits not used
for controlling the LEDs can be used for General Purpose Parallel
Input/Output (GPIO) expansion which provides a simple solution
when additional I/O is needed for ACPI power switches, sensors,
push-buttons, alarm monitoring, fans, etc.
The active low hardware reset pin (RESET) and Power On Reset
(POR) initializes the registers to their default state causing the bits
to be set high (LED off).
Three hardware address pins on the PCA9531 allow eight devices
to operate on the same bus.
ORDERING INFORMATION
PACKAGES
TEMPERATURE RANGE
ORDER CODE
TOPSIDE MARK
16-pin plastic SO
-40 to +85 °C
PCA9531D
PCA9531D
16-pin plastic TSSOP
-40 to +85 °C
PCA9531PW
PCA9531
16-pin plastic HVQFN
-40 to +85 °C
PCA9531BS
9531
Standard packing quantities and other packaging data is available at www.philipslogic.com/packaging.
I2C is a trademark of Philips Semiconductors Corporation.
DRAWING NUMBER
SOT109-1
SOT403-1
SOT629-1
2003 Nov 10
2

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Philips Semiconductors
8-bit I2C LED dimmer
Product data
PCA9531
PIN CONFIGURATION — SO, TSSOP
PIN CONFIGURATION — HVQFN
A0 1
A1 2
A2 3
LED0 4
LED1 5
LED2 6
LED3 7
VSS 8
16 VDD
15 SDA
14 SCL
13 RESET
12 LED7
11 LED6
10 LED5
9 LED4
SW02039
Figure 1. Pin configuration — SO, TSSOP
PIN DESCRIPTION
SO, TSSOP
PIN
NUMBER
HVQFN
PIN
NUMBER
1 15
2 16
31
4, 5, 6, 7
2, 3, 4, 5
86
9, 10, 11, 12 7, 8, 9, 10
13 11
14 12
15 13
16 14
SYMBOL
A0
A1
A2
LED0-3
VSS
LED4-7
RESET
SCL
SDA
VDD
A1 A0 VDD SDA
A2 1
LED0 2
LED1 3
LED2 4
12 SCL
11 RESET
10 LED7
9 LED6
LED3 VSS LED4 LED5
TOP VIEW
su01667
Figure 2. Pin configuration — HVQFN
FUNCTION
Address input 0
Address input 1
Address input 2
LED drivers 0-3
Supply ground
LED drivers 4-7
Active low reset input
Serial clock line
Serial data line
Supply voltage
2003 Nov 10
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Philips Semiconductors
8-bit I2C LED dimmer
Product data
PCA9531
BLOCK DIAGRAM
PCA9531
SCL
SDA
INPUT
FILTERS
A2 A1 A0
I2C-BUS
CONTROL
INPUT
REGISTER
LED SELECT (LSx)
REGISTER
VDD
RESET
VSS
POWER-ON
RESET
OSCILLATOR
PRESCALER 0
REGISTER
PRESCALER 1
REGISTER
0
1
PWM0
REGISTER
PWM1
REGISTER
BLINK0
BLINK1
NOTE: ONLY ONE I/O SHOWN FOR CLARITY
Figure 3. Block diagram
LEDx
SW02040
2003 Nov 10
4

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Philips Semiconductors
8-bit I2C LED dimmer
Product data
PCA9531
DEVICE ADDRESSING
Following a START condition the bus master must output the
address of the slave it is accessing. The address of the PCA9531 is
shown in Figure 4. To conserve power, no internal pullup resistors
are incorporated on the hardware selectable address pins and they
must be pulled HIGH or LOW.
SLAVE ADDRESS
1 1 0 0 A2 A1 A0 R/W
FIXED
HARDWARE SELECTABLE
su01420
Figure 4. 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.
CONTROL REGISTER
Following the successful acknowledgement of the slave address,
the bus master will send a byte to the PCA9531 which will be stored
in the Control Register.
0 0 0 AI 0 B2 B1 B0
RESET STATE: 00h
REGISTER ADDRESS
AUTO-INCREMENT FLAG
SW01034
Figure 5. Control register
CONTROL REGISTER DEFINITION
B2
B1
B0
REGISTER
NAME
TYPE
000
INPUT
READ
001
010
011
100
101
110
PSC0
PWM0
PSC1
PWM1
LS0
LS1
READ/
WRITE
READ/
WRITE
READ/
WRITE
READ/
WRITE
READ/
WRITE
READ/
WRITE
REGISTER
FUNCTION
INPUT
REGISTER
FREQUENCY
PRESCALER 0
PWM
REGISTER 0
FREQUENCY
PRESCALER 1
PWM
REGISTER 1
LED0-LED3
SELECTOR
LED4-LED7
SELECTOR
REGISTER DESCRIPTION
The lowest 3 bits are used as a pointer to determine which register
will be accessed.
If the auto-increment flag is set, the three low order bits of the
Control Register are automatically incremented after a read or write.
This allows the user to program the registers sequentially. The
contents of these bits will rollover to ‘000’ after the last register is
accessed.
When auto-increment flag is set (AI = 1) and a read sequence is
initiated, the sequence must start by reading a register different from
the input register (B2 B1 B0 0 0 0 0).
Only the 3 least significant bits are affected by the AI flag.
Unused bits must be programmed with zeroes.
INPUT INPUT REGISTER
bit 7 6 5 4 3 2 1 0
Default X X X X X X X X
The INPUT register reflects the state of the device pins. Writes to
this register will be acknowledged but will have no effect.
PSC0 FREQUENCY PRESCALER 0
bit 7 6 5 4 3 2 1 0
default 0 0 0 0 0 0 0
PSC0 is used to program the period of the PWM output.
0
The
period
of
BLINK0
+
(PSC0 ) 1)
152
PWM0 PWM REGISTER 0
bit 7 6 5 4 3 2 1 0
default 1 0 0 0 0 0 0 0
The PWM0 register determines the duty cycle of BLINK0. The
outputs are LOW (LED on) when the count is less than the value in
PWM0 and HIGH (LED off) when it is greater. If PWM0 is
programmed with 00h, then the PWM0 output is always HIGH (LED
off).
The duty cycle of BLINK0 is:
PWM0
256
PSC1 FREQUENCY PRESCALER 1
bit 7 6 5 4 3 2 1 0
default 0 0 0 0 0 0
PSC1 is used to program the period of PWM output.
0
0
The
period
of
BLINK1
+
(PSC1 ) 1)
152
PWM1 PWM REGISTER 1
bit 7 6 5 4 3 2 1 0
default 1 0 0 0 0 0 0 0
The PWM1 register determines the duty cycle of BLINK1. The
outputs are LOW (LED on) when the count is less than the value in
PWM1 and HIGH (LED off) when it is greater. If PWM1 is
programmed with 00h, then the PWM1 output is always HIGH (LED
off) .
The duty cycle of BLINK1 is:
PWM1
256
LS0 LED0-3 SELECTOR
LED 3
LED 2
LED 1
LED 0
bit 7 6 5 4 3 2 1 0
default 0 0 0 0 0 0 0 0
LS1 LED4-7 SELECTOR
LED 7
LED 6
LED 5
LED 4
bit 7 6 5 4 3 2 1 0
default 0 0 0 0 0 0 0 0
The LSx LED select registers determine the source of the LED data.
00 = Output is set Hi-Z (LED off - default)
01 = Output is set low (LED on)
10 = Output blinks at PWM0 rate
11 = Output blinks at PWM1 rate
2003 Nov 10
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