NXP Semiconductors PCA9509DP,118

Overview

The PCA9509DP,118 from NXP Semiconductors is a bidirectional I²C-bus/SMBus level-translating repeater enabling 1.35 V–1.9 V low-voltage processors to interface with 3.0 V–5.5 V I²C/SMBus peripherals. It provides isolated buffering for SDA and SCL lines, supports arbitration and clock stretching, operates up to 400 kHz, and features lock-up-free current-sensing logic on port A. It is used in mixed-voltage embedded systems such as battery-powered sensor hubs interfacing ultra-low-power microcontrollers with legacy 3.3 V I²C sensors.

For engineers reviewing the PCA9509DP,118 datasheet, PCA9509DP,118 pinout, PCA9509DP,118 application, or PCA9509DP,118 equivalent, this device delivers verified voltage translation between sub-1.8 V logic domains and standard I²C/SMBus buses while maintaining timing integrity, supporting system-level bus extension up to 400 pF on the high-voltage side, and enabling robust multi-master interoperability without external pull-ups on the low-voltage port.

Technical Context

The PCA9509DP,118 implements dual open-drain bidirectional buffers with asymmetric input detection: port A uses a 1 mA current-source pull-up and 200 Ω pull-down with ~0.2 V VOL and 0.15 V VILc to prevent lock-up, while port B complies fully with SMBus I/O levels (0.3×VCC(B) VIL, hard 0.1 V VOL at 6 mA). Both ports remain high-impedance when unpowered.

Enable control is active-HIGH and must only transition during bus idle states; internal power-up sequencing requires VCC(A) > 0.8 V and VCC(B) > 2.5 V before driver activation. Propagation delays range from −139 ns (A→B tPLH) to 226 ns (A→B tPLH2), with transition times under 40 ns on port B and under 100 ns on port A - preserving Fast-mode timing margins across translation.

Key Specifications

Pinout & Package

TSSOP8 package (SOT505-1): plastic thin shrink small outline, 8 leads, 3 mm body width, 0.65 mm lead pitch, surface-mount compatible.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C level translation applications.

Compared with PCA9509DP,118, the SO8 variant offers easier assembly and thermal dissipation but consumes more board area, while the XQFN8 enables miniaturization at the cost of tighter manufacturing controls - all three share identical translation behavior, timing, and enable logic, making them functionally interchangeable within their respective packaging constraints.

Availability

The PCA9509DP,118 is available at Aetrix Electronics and suitable for industrial sensor hubs, automotive body control modules, medical wearables, and server management controllers requiring stable component supply across extended product lifecycles.

Supply support for PCA9509DP,118 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor leader specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in interface and power management ICs.

The PCA9509DP,118 belongs to NXP's I²C/SMBus repeater family, designed specifically to solve voltage-domain bridging challenges in mixed-supply embedded systems while preserving protocol integrity and timing compliance.

FAQ

What is the minimum operating voltage on port A for PCA9509DP,118?

The PCA9509DP,118 supports port A supply voltages as low as 1.0 V when VCC(B) ≥ 3.0 V, per Table 5 in the datasheet. Below 1.35 V, the current-source pull-up decreases with temperature, but the device remains functional down to 0.95 V in non-enable/disable scenarios - however, 1.0 V is the guaranteed minimum for full specification compliance across −40 °C to +85 °C.

Does PCA9509DP,118 require external pull-up resistors on port A?

No, the PCA9509DP,118 does not require external pull-up resistors on port A because it integrates a 1 mA current-source pull-up on each A1 and A2 line. This eliminates BOM components and layout area while ensuring reliable LOW-to-HIGH transitions even at 1.35 V, unlike resistor-based solutions that would draw excessive current at low voltages.

Can PCA9509DP,118 be used with I²C Fast-mode Plus (1 MHz) devices?

No, the PCA9509DP,118 is rated for up to 400 kHz operation only. Its propagation delays (up to 226 ns) and transition times exceed timing budgets for Fast-mode Plus (1 MHz), which requires <120 ns rise/fall times and stricter setup/hold margins. Using it beyond 400 kHz risks data corruption or arbitration failure.

How does PCA9509DP,118 prevent bus lock-up during contention?

The PCA9509DP,118 prevents lock-up by implementing asymmetric voltage thresholds: its port A output LOW is ~0.2 V, while the input recognition threshold (VILc) is ~0.15 V - creating a 50 mV guard band. This ensures an internally driven LOW is not misinterpreted as an input LOW, breaking the feedback loop that causes traditional open-drain lock-up.

Is PCA9509DP,118 compatible with SMBus alert response protocol?

Yes, the PCA9509DP,118 transparently passes SMBus ALERT signals because it supports full bidirectional buffering of SDA and SCL with protocol-agnostic timing. Its lock-up-free design and support for arbitration and clock stretching ensure correct handling of SMBus Alert Response Address (ARA) transactions without modification or additional logic.