STMicroelectronics STLD40DPUR

Overview

STLD40DPUR from STMicroelectronics is a PFM-mode inductor-switch boost controller IC designed to drive up to 10 white LEDs in series for LCD backlighting. It operates from 3.0 V to 5.5 V input, delivers up to 37 V output, regulates 20 mA LED current, and features adjustable peak inductor current limit (0.2–1 A), OVP with 1.5 V hysteresis, and PWM dimming via EN pin. Used in mobile phone and PDA backlight systems.

For engineers reviewing the STLD40DPUR datasheet, STLD40DPUR pinout, STLD40DPUR application, or STLD40DPUR equivalent, key selection criteria include its QFN8 (3 × 3 mm) package, 250 ns minimum OFF time, 5.5 µs maximum ON time, 75–80% efficiency across input range, and integrated OVP restart behavior.

Technical Context

The STLD40DPUR implements a discontinuous conduction mode (DCM) PFM boost architecture with internal temperature- and supply-compensated current sensing. Regulation is achieved by monitoring voltage across RLED at the FB pin against a 130–200 mV reference, triggering switch turn-on when feedback drops below threshold.

Its embedded MOSFET has 0.4 Ω RDSON at 5.5 V, supports up to 1 A peak inductor current (set via external RSET), and includes fixed 250 ns TOFF_MIN and 5.5 µs TON_MAX timing constraints to stabilize switching frequency under varying load and input conditions.

Key Specifications

Pinout & Package

STLD40DPUR is housed in a thermally enhanced QFN8 package (3 mm × 3 mm, 0.9 mm height) with exposed thermal pad (PGND) for improved power dissipation. Pin 5 is NC; all other pins are electrically active and validated per ST's Doc ID 12203 Rev 7.

Key Features

Applications

Availability

STLD40DPUR is available at Aetrix Electronics and suitable for mobile phone backlighting, PDA display power, and industrial handheld terminal designs requiring stable component supply, guaranteed QFN8 packaging, and long-term production continuity.

Supply support for STLD40DPUR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The STLD40D product line targets low-power, space-constrained LED backlight applications where high-voltage boost capability, small footprint, and battery-efficient operation are critical design requirements.

FAQ

What is the recommended RSET value for driving 10 white LEDs at 20 mA?

For 20 mA LED current with 10-series white LEDs (37 V max), ST recommends RSET = 100 kΩ to set peak inductor current near 0.4 A - balancing inductor size, efficiency, and thermal margin. This value is confirmed in Table 6 of Doc ID 12203 Rev 7 for 4.7 µH inductors and 8 Ω RLED.

Can STLD40DPUR operate with input voltage below 3.0 V?

No. Absolute maximum ratings specify VI min = 3.0 V, and electrical characteristics are only guaranteed within 3.0–5.5 V. Operation below 3.0 V may cause failure to start, unstable regulation, or undefined OVP behavior - not supported per ST's characterization.

Is the PGND pad required to be connected to PCB ground?

Yes. The exposed thermal pad (PGND) must be soldered to a dedicated PCB ground plane with ≥4 thermal vias. ST specifies this in Section 8 (Package mechanical data) and Figure 16 for thermal resistance (RthJA = 52 °C/W) and EMI performance - floating the pad degrades reliability and efficiency.

Does STLD40DPUR support analog dimming via voltage on the EN pin?

No. EN is a digital enable input with logic thresholds (VIL ≤ 0.3 V, VIH ≥ 1.2 V). Dimming is implemented exclusively via PWM applied to EN - no linear analog dimming capability is provided or characterized in the datasheet.