onsemi 2SC3646S-TD-E

Overview

2SC3646S-TD-E from onsemi is an NPN bipolar junction transistor rated for −100 V V_CEO, 1 A continuous collector current, and low 0.1–0.4 V V_CE(sat) at I_C = −400 mA / I_B = −40 mA. It features 120 MHz f_T, 8.5 pF C_ob, and SOT-89 surface-mount package, used in high-density DC-DC converter switching stages and power supply control circuits.

For engineers reviewing the 2SC3646S-TD-E datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CE(sat) performance under pulsed load conditions, h_FE rank consistency (R/S/T), thermal derating on ceramic substrate, and SOT-89 mechanical compatibility with automated assembly.

Technical Context

This NPN transistor employs onsemi's FBET and MBIT processes to achieve high breakdown voltage (−120 V V_CBO) and fast switching (t_on = 80 ns, t_f = 50 ns) while maintaining low saturation voltage. Its design targets discrete switching in compact hybrid ICs where space-constrained layouts require ultrasmall SOT-89 footprint and high-current capability.

Electrical behavior is characterized at T_A = 25°C with defined test conditions: h_FE measured at V_CE = −5 V / I_C = −100 mA; f_T at V_CE = −10 V / I_C = −100 mA; V_CE(sat) and V_BE(sat) tested under forced β = 10 drive (I_C = −400 mA, I_B = −40 mA).

Key Specifications

Pinout & Package

SOT-89 (Case 419AU), 4.50 × 2.50 × 1.50 mm, 3-terminal surface-mount package with exposed collector tab for thermal enhancement.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD127G and ZTX653, the 2SC3646S-TD-E delivers superior high-frequency switching performance and tighter V_CE(sat) control at 400 mA, making it optimal for space-constrained, medium-voltage DC-DC stages where efficiency and layout density are critical.

Availability

2SC3646S-TD-E is available at Aetrix Electronics and suitable for DC-DC converter switches, linear regulator pass elements, LED constant-current drivers, and high-voltage interface buffers requiring stable component supply and full traceability.

Supply support for 2SC3646S-TD-E 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The 2SC3646S-TD-E belongs to onsemi's PCP (Power Control Product) family, engineered for discrete high-voltage switching in compact hybrid ICs and power modules where thermal performance and small footprint are essential.

FAQ

What is the maximum safe operating voltage for 2SC3646S-TD-E in continuous DC applications?

The 2SC3646S-TD-E has a guaranteed V_CEO rating of −100 V and V_CBO of −120 V at T_A = 25°C. For reliable long-term operation, design voltage stress should remain ≤80% of V_CEO (i.e., ≤−80 V) with appropriate derating for temperature and transients. The 2SC3646S-TD-E must not be operated beyond its absolute maximum ratings even momentarily.

Does 2SC3646S-TD-E support pulsed current operation above its 1 A continuous rating?

Yes - the 2SC3646S-TD-E supports I_CP = −2 A for short pulses (≤1 ms duty cycle), as specified in its Absolute Maximum Ratings table. This capability enables use in peak-current-mode controllers and overload protection circuits. Thermal limits still apply: pulse operation requires verification of junction temperature rise using the 1.3 W ceramic-substrate dissipation rating.

How is h_FE ranked for 2SC3646S-TD-E, and how does it affect circuit design?

The 2SC3646S-TD-E is binned into h_FE ranks R (100–200), S (140–280), and T (200–400) at I_C = −100 mA / V_CE = −5 V. Designers must select bias resistors based on the minimum h_FE of the chosen rank. For example, rank R requires ≥10× higher base drive current than rank T to maintain saturation at 400 mA collector current. The 2SC3646S-TD-E marking "CB" indicates its rank is documented per lot code.

Can 2SC3646S-TD-E be used in place of 2SA1416S-TD-E in the same circuit?

No - the 2SC3646S-TD-E is NPN while the 2SA1416S-TD-E is PNP; they are complementary devices with opposite polarity and cannot substitute directly. Swapping them would reverse current flow and bias requirements. Both share the same SOT-89 package and pinout (Base/Collector/Emitter = Pin 1/2/3), but their electrical roles are inverted. The 2SC3646S-TD-E must be used only in NPN-configured circuits.

What thermal performance can be expected from 2SC3646S-TD-E on standard FR-4 PCB?

onsemi specifies the 1.3 W dissipation rating for mounting on a 250 mm² ceramic substrate (0.8 mm thick). On standard 1 oz. FR-4 with 25 mm² copper pour, thermal resistance rises significantly - typical θ_JA exceeds 200°C/W. Therefore, continuous 1 A operation on FR-4 is not recommended. Derate to ≤300 mA for ambient temperatures >50°C unless additional copper area or thermal vias are implemented. The 2SC3646S-TD-E's exposed collector tab must be soldered to a thermal pad for any meaningful heat transfer.