PCA9621

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© NXP B.V. 2011. All rights reserved.

Product data sheet

Rev. 1 — 9 March 2011

9 of 18

NXP Semiconductors

PCA9621

65 mA 8-bit 2-wire bus output port

11. Application information

Figure 11 shows the PCA9621 in conjunction with the PCA9646 bus multiplexer in a LED

drive application. Each PCA9621 can drive 8 LEDs, and using the address pins on the IC,

up to 8 uniquely addressed devices can sit on one bus branch. The PCA9646 has four

such outputs, giving 256 LEDs in the structure shown.

By additionally using the address pins on the PCA9646, the entire structure may be

repeated 8 times, allowing 2048 LEDs to be uniquely driven. By additionally placing

PCA9646’s in series (refer to the PCA9646 data sheet), the structure may be further

extensively multiplied into a huge array.

Fig 11. PCA9621 in a large LED array

002aaf397

BUS MASTER

U2

SCL

SDA

R8

SC0

SD0

SCL

SDA

PCA9646

SC0

SD0

U1

RESET

5 V

PCA9621

U3

U10

R7

R1

R2

SC2

SD2

SC2

SD2

R3

R4

SC3

SD3

SC3

SD3

R5

R6

buses SC2/SD2, SC3/SD3

as shown for

SC0/SD0, SC1/SD1

Entire structure can be repeated

8 times using PCA9646 address pins

(further expansion possible).

A0

A1

A2

R10

SC1

SD1

SC1

SD1

PCA9621

U11

U18

R9

8

P[7:0]

8 LEDs

8

P[7:0]

8 LEDs

8

× PCA9621

each with

8 LEDs = 64 LEDs

PCA9621

8

P[7:0]

8 LEDs

PCA9621

8

P[7:0]

8 LEDs

8

× PCA9621

each with

8 LEDs = 64 LEDs