onsemi CS3972YDW16

Overview

CS3972YDW16 from ON Semiconductor is a 1.25A, 60V-input, current-mode switching regulator IC with an integrated 75V NPN power switch, 1.24V precision reference, 40kHz fixed-frequency oscillator, and variable current limit via external voltage clamp. It supports buck, boost, forward, and flyback topologies in industrial power supplies requiring wide input range and thermal robustness.

For engineers reviewing the CS3972YDW16 datasheet, pinout, applications, or equivalent options, key selection criteria include its 16-lead SO wide package thermal performance (R_ΘJA = 105°C/W), 6mA quiescent supply current at 3V input, and VC-pin-based synchronization capability for frequency adjustment between 50–70kHz.

Technical Context

The CS3972YDW16 implements peak-current-mode control using an internal 0.11Ω sense resistor and transconductance error amplifier (2400–7000 µmho) referenced to a trimmed 1.24V bandgap. Its anti-saturation circuitry maintains the NPN switch near quasi-saturation to minimize turn-off delay and conduction loss.

Protection is implemented via under-voltage lockout (min 2.6V start-up), over-temperature shutdown (T_J > 150°C), and externally adjustable current limiting using a voltage clamp on the VC pin - with distinct current limit thresholds depending on duty cycle (e.g., 1.25–3.00A at ≤50% duty, 0.50–2.50A at 80% duty for the 16L SO wide variant).

Key Specifications

Pinout & Package

CS3972YDW16 uses a 16-lead surface-mount SO wide (DW) package per JEDEC MS-013, with 10.50 × 10.10 mm body, 1.27 mm lead pitch, and exposed pad not present. Pin 1 is Gnd (logic ground); pins 4 and 7 are VSW and VIN respectively; E1 (pin 6) and E2 (pin 14) are dedicated emitter terminals tied internally to Gnd in this package configuration.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar switching regulator applications.

Compared with UC3842N and LM2596T-5.0, the CS3972YDW16 uniquely combines integrated 75V NPN switching, VC-programmable current limiting, and 16-lead SO wide thermal performance - making it suitable for ruggedized, adjustable-output industrial converters where layout space and transient resilience are prioritized over ultra-high frequency.

Availability

CS3972YDW16 is available at Aetrix Electronics and suitable for industrial DC-DC converters, automotive body control modules, and telecom power supplies requiring stable component supply and long-term lifecycle support.

Supply support for CS3972YDW16 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

ON Semiconductor (now onsemi) is a global semiconductor supplier specializing in power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The CS3972YDW16 belongs to ON Semiconductor's legacy high-voltage current-mode controller product line, designed for rugged, wide-input-range offline and DC-DC converter applications where integration, thermal reliability, and transient tolerance are critical.

FAQ

What is the maximum input voltage rating for the CS3972YDW16?

The CS3972YDW16 has an absolute maximum input voltage rating of 60V DC, with a transient rating of 60V (tr=10µs, tf=400ms). Its internal 75V NPN switch provides sufficient margin for typical 48V or 24V systems experiencing line surges. Operation above 60V violates Absolute Maximum Ratings and may cause permanent damage to the CS3972YDW16.

Does the CS3972YDW16 require an external transistor in buck topology?

No, the CS3972YDW16 integrates a 75V, 1.25A NPN power switch, eliminating the need for an external transistor in standard buck, boost, or flyback configurations. The VSW pin directly connects to the inductor or transformer primary, and the internal switch handles both conduction and current sensing via its emitter resistors - a key differentiator from controller-only ICs like UC3842N.

How is current limiting configured on the CS3972YDW16?

Current limiting on the CS3972YDW16 is configured via the VC pin: applying a DC voltage between 0.6V and 1.25V sets the current limit threshold, with transconductance of 2A/V. For example, 1.0V on VC yields ~2.0A limit. The limit also varies with duty cycle - e.g., 0.50–2.50A at 80% duty - and is validated specifically for the 16L SO wide package per datasheet Note 1.

What is the purpose of the E1 and E2 pins on the CS3972YDW16?

E1 (pin 6) and E2 (pin 14) are emitter terminals of the internal NPN switch. In the CS3972YDW16's 16L SO wide package, both are internally bonded to Gnd and serve as low-inductance return paths for the current-sense resistor (0.11Ω) and switch emitter. They must be connected to the same ground plane as pin 1 (Gnd) to maintain accurate current sensing and thermal stability.

Is the CS3972YDW16 still recommended for new designs?

No - the CS3972YDW16 is marked "DEVICE NOT RECOMMENDED FOR NEW DESIGN" in its official datasheet (Rev. 9, December 2001). While fully functional and supported for legacy repair and continuity, new designs should consider modern alternatives such as the NCP1252 or UCC28C4x series for improved efficiency, smaller footprint, and active manufacturer support. The CS3972YDW16 remains available for existing production.