Build with PCA9509 — Datasheet Specs & AI Design Help

00 — Overview

What the PCA9509 does

The PCA9509 is a level translating I2C-bus/SMBus repeater that interfaces low-voltage 2-wire serial buses with standard I/O. It spans variants including the PCA9509A for lower voltage applications and comes in SO8, TSSOP8, and XQFN8 packages. The device supports a 0Hz to 400kHz clock frequency with voltage translation from 1.35V to 5.5V across its ports. It features bidirectional buffering for data and clock lines, accommodating a maximum capacitance of 400pF on the higher voltage side. The PCA9509 requires no external pull-up resistors on the lower voltage port and ensures lock-up free operation. It supports arbitration and clock stretching while remaining high-impedance when unpowered, making it ideal for extending bus length and connecting mixed-voltage systems.

Next step

Start building with PCA9509 → Every number above is cited straight from the datasheet — ask what they mean for your design, and the assistant answers from the same source documents.

01 — Key specifications

Datasheet parameters

Datasheet parameters for PCA9509
Parameter	Min	Typ	Max	Conditions	Source
quiescent current	1.25 mA	3 mA	5 mA	all port A static LOW; icc(a); Supplies	NXP datasheet, p. 8 — Table 5. Static characteristics
operating temperature (abs max)	-40 °C	—	85 °C	operating in free air; tamb; Limiting values	NXP datasheet, p. 7 — Table 4. Limiting values
power dissipation (abs max)	—	—	100 mW	ptot; Limiting values	NXP datasheet, p. 7 — Table 4. Limiting values
input capacitance	—	2 pF	3 pF	VI = 3.0 V or 0 V; ci; Enable	NXP datasheet, p. 8 — Table 5. Static characteristics
output capacitance	—	6 pF	7 pF	cio; Input and output of port A (A1 to A2)	NXP datasheet, p. 8 — Table 5. Static characteristics
propagation delay	63 ns	86 ns	140 ns	port B to port A; tphl	NXP datasheet, p. 10 — Table 6. Dynamic characteristics
data rate	0 bps	—	400 kbps	clock frequency	NXP datasheet, p. 1
output voltage low	—	200 mV	300 mV	[5]; vol; Input and output of port A (A1 to A2)	NXP datasheet, p. 8 — Table 5. Static characteristics
channel count	—	2	—		NXP datasheet, p. 3
driver count	—	2	—		NXP datasheet, p. 3

02 — Alternatives

Closest matches to PCA9509

MAX3232 2.8× higher propagation delay, 2.0× higher output voltage low, 1.8× higher output current

SN65HVD3082E 6.4× higher propagation delay, 3.5× higher input capacitance, 2.0× higher power dissipation

SP3485E 13.6× lower propagation delay, 2.0× higher output voltage low, 1.7× higher output current

SP3222ECA-L 2.8× higher propagation delay, 1.8× higher output current, 1.6× higher operating temperature

ADM2483BRW 4.0× higher propagation delay, 2.5× higher data rate, 2.3× higher output current

GM3085E 5.0× higher data rate, 3.2× lower quiescent current, 2.6× higher output current

MAX485ESA 12.5× higher data rate, 3.6× lower propagation delay, 2.0× higher output voltage low

PCA9517D 3.3× higher quiescent current, 3.0× higher input capacitance, 2.6× higher output voltage low

03 — FAQ

Frequently asked questions

What is the channel count of the PCA9509?

The channel count is 2.

What is the data rate when the clock frequency is specified?

The data rate is 400 kbps at the clock frequency.

What is the driver count for the PCA9509?

The driver count is 2.

What is the input capacitance when VI = 3.0 V or 0 V and ci; Enable?

The input capacitance is 2 pF.

What is the maximum operating temperature for the PCA9509 when operating in free air?

The maximum operating temperature is 85 °C.

What is the output capacitance (Cio) for the input and output of port A (A1 to A2)?

The output capacitance (Cio) for the input and output of port A (A1 to A2) is 6 pF.

What is the output voltage low specification for the input and output of port A (A1 to A2)?

The output voltage low is 200 mV.

What is the power dissipation (ptot) under Limiting values?

The power dissipation (ptot) under Limiting values is 100 mW.

What is the propagation delay from port B to port A (tphl) for the PCA9509?

The propagation delay from port B to port A (tphl) is 86 ns.

What is the quiescent current when all port A is static LOW?

The quiescent current is 3 mA (icc(a)) with supplies.