Microchip Technology AT9933LG-G

Overview

AT9933LG-G from Microchip Technology is a hysteretic boost-buck (Ćuk) LED driver IC designed for constant-current control of high-brightness LED lamps. It regulates both input and output currents via dual hysteretic comparators, supports 8V–75V input voltage, delivers up to 125°C ambient operation, and enables PWM dimming with 0%–100% duty cycle control - ideal for automotive and industrial LED lighting systems.

For engineers reviewing the AT9933LG-G datasheet, AT9933LG-G pinout, AT9933LG-G application, or AT9933LG-G equivalent, this page provides verified technical context, validated pin functions, confirmed thermal and current-sensing specifications, and real-world design constraints for Ćuk topology implementation under surge, cold-crank, and overvoltage conditions.

Technical Context

The AT9933LG-G implements two independent hysteretic current-mode controllers-one for input current (CS1) and one for output current (CS2)-with 100 mV internal hysteresis and 150–250 ns propagation delay. Its AND-gated output drives an external N-channel MOSFET via a 0.165 A source/sink gate driver with 30–50 ns rise/fall times into 500 pF.

It integrates a 7.5 V internal linear regulator (7–9 V typical output) powered from VIN, featuring 6.35–7.05 V UVLO threshold and 500 mV hysteresis. The REF pin supplies a trimmed 1.25 V reference (±3.5% over –40°C to +125°C) with ±500 µA load capability for setting current thresholds in the Ćuk converter.

Key Specifications

Pinout & Package

AT9933LG-G is housed in an 8-lead SOIC package (JEDEC MS-012AC, 3.9 mm × 4.9 mm × 1.75 mm), RoHS-compliant and Pb-free (G suffix), rated for 700 mW power dissipation at TA = +25°C and θJA = 101°C/W on FR-4 board.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT3762EFE#PBF and UCC28810DR, AT9933LG-G uniquely provides simultaneous input and output current regulation in a Ćuk topology - enabling superior surge tolerance and failure-safe operation without added compensation or protection components.

Availability

AT9933LG-G is available at Aetrix Electronics and suitable for automotive lighting, industrial LED fixtures, outdoor streetlights, and UV-C disinfection modules requiring stable component supply across extended temperature and surge-prone environments.

Supply support for AT9933LG-G 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

Microchip Technology is a global provider of microcontrollers, analog devices, and interface ICs, with leadership in embedded control and power management solutions.

The AT9933LG-G belongs to Microchip's high-reliability LED driver controller product line, engineered specifically for robust, low-EMI constant-current regulation in DC-input Ćuk-based LED lighting systems operating under harsh thermal and electrical conditions.

FAQ

What is the maximum input voltage the AT9933LG-G can withstand?

The AT9933LG-G supports an absolute maximum VIN of +75 V relative to GND, with functional operation specified from 8 V to 75 V DC. This 75 V rating applies to the VIN pin directly and enables use in 48 V industrial systems and 24 V automotive applications with headroom for load-dump transients. Exceeding 75 V may cause permanent damage per Absolute Maximum Ratings.

Does the AT9933LG-G require external loop compensation?

No, the AT9933LG-G does not require external loop compensation because it uses patent-pending hysteretic current-mode control with dual comparators - one for input current (CS1) and one for output current (CS2). This architecture inherently stabilizes the Ćuk converter without traditional Type II/III compensation networks, reducing component count and design complexity.

How does the AT9933LG-G handle cold-crank conditions in automotive applications?

The AT9933LG-G handles cold-crank by allowing VIN to drop below 8 V while maintaining operation - provided VDD remains above the 6.35–7.05 V UVLO threshold. As shown in Figure 3-1, at 125°C and 5.5 mA input current, the regulator drop is ~2.7 V, enabling functional operation down to ~7.5 V VIN. For deeper cranking, VIN can be tied to the MOSFET drain via a diode and small capacitor to sustain VDD.

Can the AT9933LG-G drive multiple LED strings in parallel?

The AT9933LG-G is designed to regulate current in a single output path via CS2 feedback. Driving multiple parallel LED strings requires individual current-setting resistors (RCS2) per string or external current-mirror circuitry - otherwise mismatched forward voltages will cause current imbalance. Microchip's recommended approach is series-string configuration or dedicated per-string controllers for tight current matching.

What is the purpose of the damping circuit (RD and CD) in AT9933LG-G designs?

The RD and CD damping network across capacitor C1 in the Ćuk topology suppresses undamped oscillations between L1 and C1 that occur during output-current-controlled operation. Without damping, these oscillations cause excessive voltage stress on C1 and instability in regulation. RD and CD values are calculated per Application Note AN-H58 to ensure stable steady-state performance and prevent transformer-like ringing.