Diodes Incorporated FMMT6520TC

Overview

FMMT6520 from Diodes Incorporated is a PNP silicon planar high-voltage transistor in SOT-23 package, rated for -350V V_CEO, -500mA I_C, and 330mW power dissipation; used as a high-voltage power switch in industrial DC-DC converters and relay drivers.

For engineers reviewing the FMMT6520 datasheet, FMMT6520 pinout, FMMT6520 application, or FMMT6520 equivalent, key selection criteria include breakdown voltage margin, saturation voltage at 50mA, h_FE consistency across 1–100mA, thermal resistance to ambient, and AEC-Q101 qualification status.

Technical Context

This PNP transistor operates in linear or switching mode with guaranteed BV_CEO ≥ −350V and V_CE(sat) ≤ −500mV at I_C = −50mA/I_B = −5mA. Its f_T of 50MHz supports moderate-speed switching up to ~100kHz in hard-switched topologies.

Thermal design relies on R_θJA = 379°C/W (FR4, 1 oz Cu, still air) and R_θJL = 350°C/W to junction-to-lead; moisture sensitivity level is J-STD-020 Level 1, enabling standard reflow without baking.

Key Specifications

Pinout & Package

Package: SOT-23 - surface-mount plastic case, 0.008g weight, UL 94V-0 rated, matte tin terminals solderable per MIL-STD-202 Method 208.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage PNP transistor applications.

Compared with ZTX653, FMMT6520 provides 50V higher blocking capability critical for 240VAC-derived rails, while MMBT6520 is a form-fit-function identical variant differing only in packaging and marking-not a true alternative but a sourcing option.

Availability

FMMT6520 is available at Aetrix Electronics and suitable for industrial relay drivers, high-voltage DC-DC converters, LED string power switches, and overvoltage protection circuits requiring stable component supply and AEC-Q101 reliability assurance.

Supply support for FMMT6520 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, serving industrial, computing, consumer, and automotive markets since 1959.

The FMMT6520 belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for robust switching in harsh environments where sustained voltage stress and thermal cycling are routine.

FAQ

What is the maximum safe operating voltage for FMMT6520 in continuous DC applications?

The absolute maximum V_CEO is −350V, but design practice limits continuous operation to ≤ −280V to maintain 20% margin against process variation and temperature-induced degradation. Derating curves in DS33123 show usable V_CEO drops to −250V at T_J = +125°C, confirming −280V as the recommended DC ceiling at 25°C ambient.

Can FMMT6520 be used in linear amplifier configurations?

Yes, but only in Class-A or low-power Class-AB stages due to its 330mW power limit and wide h_FE spread (20–200). At I_C = −10mA and V_CE = −10V, it delivers <100mW dissipation, enabling stable small-signal amplification with emitter degeneration to stabilize bias.

Is FMMT6520 pin-compatible with SOT-23 NPN counterparts like FMMT618?

No - FMMT6520 is PNP with E-B-C pinout (top view), whereas FMMT618 is NPN with E-B-C reversed (C-B-E). Swapping them without board revision causes immediate reverse-bias failure. Pin compatibility exists only within complementary pairs like FMMT6517 (PNP) and FMMT6520 (PNP), not across polarity types.

Does FMMT6520 require gate/base drive conditioning for fast switching?

Yes - its base-emitter capacitance and minority-carrier storage delay demand active base pull-down (e.g., 1kΩ resistor to ground) to achieve <1µs turn-off. Without it, stored charge extends fall time, increasing switching loss. The −750mV to −900mV V_BE(sat) range also requires precise base current control to avoid overdrive-induced secondary breakdown.