NXP Semiconductors BST72A,112

Overview

BST72A,112 from NXP Semiconductors (formerly Philips) is an N-channel enhancement-mode vertical D-MOS transistor in TO-92 variant (SOT54) package, rated for 80 V V_DS, 300 mA I_D, and 0.83 W P_tot, with R_DS(on) ≤10 Ω at 150 mA/5 V. It is engineered for telephone ringer circuits, relay drivers, and high-speed line-transformer switching.

For engineers reviewing the BST72A,112 datasheet, BST72A,112 pinout, BST72A,112 application, or BST72A,112 equivalent, key selection criteria include its gate threshold voltage range (1.5–3.5 V), sub-10 ns switching times, direct CMOS/TTL interface capability, and thermal resistance of 150 K/W - critical for low-power, high-reliability discrete switching in space-constrained telephony and electromechanical control designs.

Technical Context

This device operates as a single N-channel power MOSFET with vertical D-MOS architecture, enabling fast turn-on/turn-off (t_on/t_off ≤10 ns) and no second breakdown limitation. Its gate threshold voltage (V_GS(th)) is specified between 1.5 V and 3.5 V at I_D = 1 mA, ensuring compatibility with 3.3 V and 5 V logic families.

Thermal design is constrained by R_{th j-a} = 150 K/W under standard PCB mounting (lead length ≤4 mm), and junction temperature must remain ≤150 °C. Capacitance parameters - C_iss ≤30 pF, C_oss ≤20 pF, Cr_ss ≤6 pF at V_DS = 10 V - support stable high-frequency switching in inductive load interfaces.

Key Specifications

Pinout & Package

Package: TO-92 variant (SOT54), plastic single-ended leaded through-hole package with 3 leads on-circle; dimensions per IEC outline (D = 4.8 mm, E = 4.2 mm, L = 14.5 mm).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar N-channel D-MOS switching applications.

Compared with BS170,112 and 2N7002,215, the BST72A,112 provides superior voltage margin (80 V) and through-hole reliability for legacy telephony hardware, while maintaining identical drive compatibility and switching speed - making it the preferred choice for new builds requiring field-proven robustness in ringing and relay applications.

Availability

BST72A,112 is available at Aetrix Electronics and suitable for telephone ringer circuits, electromechanical relay drivers, and line-transformer switching applications requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for BST72A,112 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 formed from the spin-off of Philips Semiconductors in 2006, specializing in secure connectivity solutions for automotive, industrial, and communication markets.

The BST72A,112 belongs to NXP's legacy discrete power MOSFET product line, designed specifically for robust, low-cost switching in telephony infrastructure and electromechanical control systems where reliability under transient stress is essential.

FAQ

What is the maximum drain-source voltage rating for BST72A,112?

The BST72A,112 has a maximum continuous drain-source voltage (V_DS) rating of 80 V, with a non-repetitive peak rating of 100 V for pulse widths ≤2 ms. This makes BST72A,112 suitable for telephone line ringing applications where transient voltages reach up to 90 V, provided proper clamping or timing limits are observed per the absolute maximum ratings table.

Can BST72A,112 be driven directly by a 3.3 V microcontroller GPIO?

Yes - BST72A,112 has a gate threshold voltage (V_GS(th)) range of 1.5 V to 3.5 V, and its gate leakage is ≤100 nA. A 3.3 V GPIO can reliably turn on BST72A,112 with full conduction (I_D = 150 mA) at R_DS(on) ≤10 Ω, though performance is optimized at V_GS ≥5 V. BST72A,112 does not require external level-shifting circuitry in most 3.3 V logic designs.

What is the thermal resistance from junction to ambient for BST72A,112?

The junction-to-ambient thermal resistance (R_{th j-a}) of BST72A,112 is 150 K/W when mounted on a standard PCB with lead lengths ≤4 mm (per datasheet Note 1). This value assumes no copper pour or heatsinking; adding 1 cm² of 1 oz copper connected to the source pad reduces R_{th j-a} by ~30–40 K/W. BST72A,112 must be operated within its 0.83 W P_tot limit at 25 °C ambient to avoid exceeding T_j = 150 °C.

Is BST72A,112 suitable for driving a 12 V, 200 mA relay coil?

Yes - BST72A,112 supports 300 mA DC drain current and has R_DS(on) ≤10 Ω at 150 mA/5 V. Driving a 12 V/200 mA relay results in ~2 V drop across BST72A,112 (200 mA × 10 Ω), leaving ~10 V across the coil - sufficient for reliable pull-in. Power dissipation is ~0.4 W, well within BST72A,112's 0.83 W rating at 25 °C. BST72A,112 also withstands inductive kickback via its 100 V V_DS(SM) rating.

Does BST72A,112 have built-in ESD protection?

No - BST72A,112 does not include integrated ESD protection diodes. Its gate oxide is susceptible to damage from static discharge; therefore, handling and PCB layout must follow standard MOSFET ESD precautions (e.g., grounded workstations, series gate resistors ≤100 Ω, avoidance of floating gate traces). The datasheet specifies V_GSO = ±20 V maximum, but real-world gate failure can occur at much lower voltages if ESD events are unmitigated. Always treat BST72A,112 as unprotected unless externally safeguarded.