PCA9525

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© NXP B.V. 2011. All rights reserved.

Product data sheet

Rev. 1 — 25 February 2011

11 of 22

NXP Semiconductors

PCA9525

Simple 2-wire bus buffer

Figure 15 shows the PCA9525 used with masters on both sides of the buffer. More than

one master may be used on the Sxx_IN side of the IC. However, to locate a master on the

Sxx_OUT side and have that master be able to communicate with devices on the Sxx_IN

side, it must either have direct control over the direction pin (DIR) of the PCA9525, or it

must request another controlling master to change the direction. In Figure 15, U4 uses an

IRQ to signal to U2 that is requests a direction change. Once in control, it could

alternatively use the bus to signal ‘release of control’.

Fig 14. PCA9525 typical buffer application

002aaf342

BUS MASTER

U3

SCL

SDA

R4

1.1 k

Ω

SCL

SDA

SCL_IN

SDA_IN

PCA9525

SCL_OUT

SDA_OUT

U1

EN

DIR

3.3 V

MASTER/

SLAVE

U4

SLAVE

U5

SLAVE

U6

R3

1.1 k

Ω

R1

1.1 k

Ω

R2

1.1 k

Ω

R4

110

Ω

SCL

SDA

SCL_IN

SDA_IN

PCA9605

SCL_OUT

SDA_OUT

U2

EN

DIR

SLAVE

U7

SLAVE

U8

R5

110

Ω

up to 400 pF load

(PCA9525)

or 4 nF load if only

PCA9605's used

(R1 and R2 = 110

Ω)

up to 400 pF load (PCA9525)

up to 4 nF load (PCA9605)