Diodes Incorporated ZXGD3109N8TC

Overview

ZXGD3109N8TC from Diodes Incorporated is a synchronous MOSFET controller in SO-8 package designed to replace ideal diodes in flyback and resonant converters. It features 200V drain voltage rating, 30ns typical turn-off propagation delay, programmable minimum on/off times (0.34µs/3µs typ), and light-load detection for efficiency optimization in auxiliary power supplies and PoE devices.

For engineers reviewing the ZXGD3109N8TC datasheet, ZXGD3109N8TC pinout, ZXGD3109N8TC application, or ZXGD3109N8TC equivalent, key selection criteria include VD-VS sensing thresholds (−150mV turn-on, −4mV high-voltage turn-off), 2A/4A gate source/sink capability, SO-8 thermal resistance (173°C/W with 10mm×10mm heatsinks), and UVLO threshold (2.8–3.2V) with 200mV hysteresis.

Technical Context

The ZXGD3109N8TC implements a voltage-sensing architecture that monitors VD–VS differential to control gate drive timing. Its comparator-based detector triggers gate activation when VD falls 150mV below VS and deactivates when VD rises above VS by 4mV (at VCC > 4.3V), enabling precise synchronous rectification in DCM/CrCM topologies.

Intelligent timing control includes programmable TON (via RTON) and TOFF (via RTOFF), plus integrated light-load detection that disables switching when MOSFET conduction time drops below TON, reducing switching losses at no load. The TOFF/EN pin serves dual functions: setting minimum off-time and enabling/disabling the device via voltage thresholds (1.4V active, 0.6V sleep).

Key Specifications

Pinout & Package

SO-8 surface-mount package with exposed thermal pad (not electrically connected), 1.27mm pitch, JEDEC MS-012AC compliant, moisture sensitivity level 1, and RoHS-compliant matte tin plating.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous rectifier controller applications.

Compared with MP6908GJ-Z and UCC24612-2QDRQ1, the ZXGD3109N8TC uniquely balances 200V drain tolerance, programmable timing, and light-load detection-making it optimal for high-efficiency consumer/server flyback and resonant converters where BOM count and no-load power matter most.

Availability

ZXGD3109N8TC is available at Aetrix Electronics and suitable for power adaptors, auxiliary power supplies, and PoE power devices requiring stable component supply and legacy design support despite discontinuation status.

Supply support for ZXGD3109N8TC 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, with design centers across Asia and manufacturing in Taiwan, China, and the US.

The ZXGD product line targets high-efficiency power conversion, specifically synchronous rectification controllers optimized for flyback and resonant topologies in consumer, computing, and industrial power supplies.

FAQ

What is the recommended layout practice for the VD pin to ensure noise immunity?

Route the VD trace directly from the MOSFET drain to the IC pin with minimal length and no vias, placing it adjacent to the transformer secondary winding pad. Use a guard ring tied to VS around the VD trace and avoid routing near switching nodes or gate drivers. The datasheet specifies this reduces false triggering caused by dV/dt-induced coupling.

How does Light Load Detection (LLD) interact with the TON resistor setting?

LLD activates when the measured MOSFET on-time falls below the TON window set by RTON. If RTON is set to 8.25kΩ (0.34µs), LLD engages at lighter loads than with 100kΩ (3.8µs). This allows designers to trade off minimum load efficiency against transient response speed during load steps.

Can the ZXGD3109N8TC be used with 15V VCC supply?

No-absolute maximum VCC is 15V, but recommended operating range is 4.5–12V. Exceeding 12V risks exceeding internal regulator limits and increasing junction temperature beyond safe margins. For 15V rails, the datasheet mandates an external LDO (e.g., ZXTR2012) as shown in Figure 8.

What failure mode occurs if the PGATE capacitor is omitted?

Omitting the 100nF PGATE capacitor causes gate drive instability due to insufficient local charge reservoir. This results in VCC droop during high-current gate transitions, leading to erratic turn-on/turn-off timing, increased EMI, and potential MOSFET shoot-through during overlap events.