STMicroelectronics ST5R33MTR

Overview

ST5R33MTR from STMicroelectronics is a micropower VFM step-up DC/DC converter optimized for battery-powered systems requiring 3.3 V regulated output at up to 100 mA, ultra-low 17 µA quiescent supply current, and start-up from as low as 0.8 V (VIN–VF). It integrates a 850 mΩ internal power switch, operates at 150 kHz max oscillator frequency, and delivers 83% typical efficiency at 50 mA load-enabling extended runtime in pagers, wireless telephones, and palmtop computers.

For engineers reviewing the ST5R33MTR datasheet, ST5R33MTR pinout, ST5R33MTR application, or ST5R33MTR equivalent, key selection criteria include verified start-up voltage (0.8–1.2 V), ±5% output accuracy (3.135–3.465 V), SOT23-5L package constraints, and VFM control architecture enabling stable light-load efficiency without external compensation.

Technical Context

The ST5R33MTR employs a fixed-T_ON (5 µs typ.), variable-T_OFF VFM control architecture where switching frequency adjusts dynamically with load: minimum T_OFF is 1.7 µs (150 kHz max), and duty cycle remains stable at 77% across temperature. Error amplifier compares feedback from an internal resistive divider against a bandgap reference (V_REF) to regulate output.

Internal current limiting acts via V_LX sensing-RDSON × I_SW triggers shutdown when peak inductor current exceeds safe limits. The VOUT pin doubles as supply rail, so the 3.3 V version enables lower RDSON (vs. 2.5 V variants) and slightly higher efficiency due to elevated internal bias voltage.

Key Specifications

Pinout & Package

SOT23-5L package: 2.8–3.0 mm × 1.5–1.75 mm footprint, 1.0–1.45 mm height, with exposed pad not electrically connected. Pin 1 marked by dot; pins numbered counterclockwise from top-left (top view).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-up DC/DC converter applications.

Compared with TPS61022DRVR and MAX17222ETA+, ST5R33MTR uniquely balances 3.3 V output accuracy, 100 mA capability, sub-1.2 V start-up, and SOT23-5L integration-making it optimal for cost-sensitive, space-constrained battery equipment where all four parameters are non-negotiable.

Availability

ST5R33MTR is available at Aetrix Electronics and suitable for wireless telephones, palmtop computers, pagers, and other portable electronics requiring stable component supply with guaranteed long-term manufacturability.

Supply support for ST5R33MTR 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, power, microcontroller, and sensor solutions for automotive, industrial, and consumer markets.

The ST5R00 series was developed specifically for ultra-low-power, single-cell battery applications demanding high conversion efficiency at microampere quiescent currents and minimal external component count.

FAQ

What is the minimum input voltage required for ST5R33MTR to start switching?

The ST5R33MTR starts switching when VIN minus the forward voltage (VF) of the external Schottky diode reaches 0.8 V (typical) to 1.2 V (max), measured under 1 mA load. This means with a diode VF of 0.3 V, actual VIN start-up ranges from 1.1 V to 1.5 V. The device holds regulation down to 0.6 V (VIN–VF), enabling operation beyond initial start-up.

Can ST5R33MTR be used with ceramic output capacitors instead of tantalum?

Yes-ceramic capacitors are acceptable if ESR is ≤100 mΩ and capacitance is ≥47 µF. However, low-ESR ceramics may cause instability in VFM mode due to reduced phase margin; STMicroelectronics recommends adding a 1 Ω damping resistor in series with the capacitor or selecting X5R/X7R dielectrics with controlled ESR characteristics per AN2472 guidelines.

Is the NC pin on ST5R33MTR required to be grounded?

No-the NC pin is internally unconnected and has no electrical function. STMicroelectronics datasheet Figure 2 shows it as unassigned; it may be left floating or tied to GND for mechanical stability. Neither choice affects regulation, efficiency, or EMI performance-no current flows through this terminal under any operating condition.

How does ST5R33MTR's efficiency compare to ST5R50MTR at light loads?

At 1 mA load, ST5R33MTR achieves ~78% efficiency versus ~75% for ST5R50MTR due to lower internal RDSON (850 mΩ vs. 700 mΩ) and reduced gate drive losses at its lower output voltage. The 3.3 V version also exhibits 10% lower output ripple at same load because of reduced voltage swing across the output capacitor ESR.