Diodes Incorporated ZXSC310E5TA

Overview

ZXSC310E5TA from Diodes Incorporated (formerly Zetex Semiconductors) is a PFM-based DC-DC controller IC designed to drive external NPN switching transistors in LED boost converter topologies. It operates from 0.8V to 8V input, delivers programmable constant-current output via ISENSE pin (19mV threshold), supports shutdown control (STDN pin), and achieves up to 94% efficiency in LCD backlight circuits for digital still cameras and PDAs.

For engineers reviewing the ZXSC310E5TA datasheet, ZXSC310E5TA pinout, ZXSC310E5TA application, or ZXSC310E5TA equivalent, key selection criteria include minimum startup voltage (0.8V), standby current (<5µA), drive capability for low-V_CE(sat) transistors like FMMT618, SOT23-5 package constraints, and compatibility with Schottky diodes such as ZHCS1000 in rectified configurations.

Technical Context

The ZXSC310E5TA implements a pulse-frequency modulation (PFM) control architecture that dynamically adjusts switching frequency based on load, input voltage, and programmed peak current. Its internal comparator monitors ISENSE voltage against a 19mV reference to regulate LED current, while a monostable circuit enforces a fixed 1.7µs discharge time (T_OFF) to ensure inductor energy reset before each cycle.

It functions exclusively as a controller - not a complete driver - requiring an external NPN transistor (e.g., FMMT618) and optional Schottky diode (e.g., ZHCS1000). The VDRIVE output supplies fixed base drive current (1.5–3.5mA), enabling fast transistor turn-off (~30ns), and the STDN pin provides TTL-compatible enable/disable logic with 0.15V low and 0.7V high thresholds.

Key Specifications

Pinout & Package

SOT23-5 surface-mount package (3.0 × 2.8 × 1.3 mm), RoHS-compliant, with exposed pad not electrically connected. Pin 1 marked by dot; standard top-view orientation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LED boost controller applications.

Compared with MAX1910 and TPS61060, the ZXSC310E5TA uniquely balances ultra-low-voltage startup, discrete transistor flexibility, and PFM efficiency - making it optimal for cost-sensitive, battery-constrained LCD backlight designs where runtime and component count are prioritized over integration density.

Availability

ZXSC310E5TA is available at Aetrix Electronics and suitable for LCD backlighting in digital still cameras, PDA displays, and mobile keypad illumination requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for ZXSC310E5TA 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 acquired Zetex Semiconductors in 2008 and maintains its portfolio of high-efficiency analog and power management ICs focused on portable and battery-powered applications.

The ZXSC310E5TA belongs to Zetex's LED driver controller product line, engineered specifically for discrete-component boost converters in space-constrained, low-input-voltage backlight systems - emphasizing efficiency, simplicity, and compatibility with low-cost bipolar transistors.

FAQ

What external components are mandatory for basic ZXSC310E5TA operation?

The ZXSC310E5TA requires three mandatory external components: an NPN switching transistor (e.g., FMMT618) connected to VDRIVE and ISENSE, a current-sense resistor tied between ISENSE and GND to set LED current, and an inductor between VCC and the transistor collector. No output capacitor is needed for pulsed operation; a Schottky diode (e.g., ZHCS1000) and output capacitor are added only for DC output configurations.

Can ZXSC310E5TA drive multiple LEDs in series or parallel without redesign?

Yes - the ZXSC310E5TA supports both configurations via external circuit changes. For series LEDs, use a single sense resistor and Schottky diode to generate DC output voltage higher than the LED string V_F. For parallel LEDs, place individual sense resistors per branch or use a shared resistor with matched V_F LEDs; the controller regulates total current, so brightness uniformity depends on LED binning and thermal design.

How does the 19mV ISENSE threshold impact accuracy across temperature?

The ISENSE threshold has a guaranteed tempco of 0.4%/°C, meaning a ±25°C shift from 25°C causes ±10% variation in set current (e.g., 20mA becomes 18mA or 22mA). For precision applications, select low-tempco resistors (e.g., 25ppm/°C) and minimize thermal coupling between ISENSE node and heat sources; reference designs achieve ±5% total current error over −40°C to +85°C with proper layout.

Is ZXSC310E5TA compatible with lithium coin cell power sources?

Yes - its 0.8V minimum operating voltage allows direct use with CR2032 (nominal 3.0V, end-of-life ~2.0V) and even partially discharged BR2032 (2.4V) cells. However, maximum output power is limited by input current capability: CR2032 typically sustains <10mA continuous, so ZXSC310E5TA configurations must limit peak inductor current to ≤15mA to avoid excessive voltage sag and maintain regulation.