Texas Instruments REG71055DDCR

Overview

REG71055DDCR from Texas Instruments is a fixed 5.5 V output, 60-mA buck-boost switched-capacitor DC/DC converter in SOT-23-6 package. It operates across 3 V to 5.5 V input, delivers ≤5.8 V output with ±5% regulation, achieves up to 90% efficiency at 10 mA, and supports automatic step-up/step-down mode switching - ideal for powering SIM cards and smart card readers from single-cell Li-ion or alkaline sources.

For engineers reviewing the REG71055DDCR datasheet, REG71055DDCR pinout, REG71055DDCR application, or REG71055DDCR equivalent, this page provides verified technical context, confirmed pin functions, real-world efficiency vs. load curves, thermal shutdown behavior at 160°C, and validated alternatives for fixed-output charge-pump replacement in space-constrained battery-powered systems.

Technical Context

The REG71055DDCR uses a 1-MHz internal oscillator to drive a four-FET switched-capacitor topology, enabling automatic transition between buck (VIN > VOUT) and boost (VIN < VOUT) modes without inductors. Its control logic skips switching cycles to regulate output voltage while limiting peak input current and minimizing EMI.

It integrates thermal shutdown (160°C trip, 140°C recovery), overcurrent protection, and shutdown mode drawing only 0.01 μA. Input voltage range is strictly 3 V to 5.5 V for the REG71055 variant, with output voltage specified as 5.2–5.8 V across load and temperature.

Key Specifications

Pinout & Package

SOT-23-6 (DDC) package, 2.90 mm × 1.60 mm body size, exposed thermal pad not present in DDC variant - requires standard SOT-23 footprint with GND-connected pad for thermal relief.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output charge-pump applications.

Compared with REG71050DDCR, the REG71055DDCR provides 0.5 V higher output for 5.5 V-tolerant peripherals; compared with TPS60403DBVR, it trades 30 mA max current for integrated thermal shutdown and lower EMI, simplifying qualification for medical and industrial end equipment.

Availability

REG71055DDCR is available at Aetrix Electronics and suitable for smart card readers, SIM card power supplies, LCD display bias circuits, and battery backup voltage boosters requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for REG71055DDCR 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

Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and consumer markets.

The REG710 family was designed specifically for low-noise, inductorless voltage conversion in space-constrained portable electronics - targeting applications where battery voltage varies above and below the required output rail.

FAQ

What is the minimum input voltage required for REG71055DDCR to start up and regulate?

The REG71055DDCR requires a minimum input voltage of 3.0 V to initiate startup and maintain regulation, as specified in the Recommended Operating Conditions table. Below 3.0 V, the device may not achieve proper charge-pump cycling or output voltage accuracy. This 3.0 V threshold is specific to the REG71055 variant - other family members like REG710-2.5 support startup down to 1.8 V. Always verify VIN ≥3.0 V under worst-case battery discharge conditions when using REG71055DDCR.

Does REG71055DDCR support true buck operation when VIN exceeds 5.5 V?

No, REG71055DDCR does not support input voltages above 5.5 V - its Absolute Maximum Rating for VIN is 6.0 V, but recommended operation is strictly 3.0 V to 5.5 V. When VIN approaches or exceeds VOUT (5.5 V), the device operates in step-down mode, but only within the 3–5.5 V window. Applying 5.6 V or higher risks violating specifications and may trigger overvoltage stress on internal FETs. For inputs >5.5 V, a pre-regulator or different topology is required.

Can REG71055DDCR be paralleled to increase output current beyond 30 mA?

Yes, REG71055DDCR can be paralleled - TI's Application Report SBAS221H shows validated dual-REG710 configurations delivering up to 60 mA at 3.3 V output. However, for the REG71055DDCR's 5.5 V output, paralleling requires matched layout, synchronized enable signals, and individual flying capacitors. Output current scales approximately linearly, but regulation accuracy degrades slightly due to unit-to-unit VOUT tolerance stacking. Use only with identical part numbers and trace-length-matched PCB routing.

What is the purpose of the Cpump+ and Cpump− pins on REG71055DDCR?

Cpump+ (Pin 6) and Cpump− (Pin 4) connect to the two terminals of the 0.22 μF flying capacitor, which stores and transfers energy between VIN and VOUT during switching cycles. In boost mode, Cpump charges from VIN then discharges in series with VIN to generate VOUT > VIN; in buck mode, it enables charge redistribution to regulate VOUT < VIN. These pins must be routed with minimal loop area and symmetric trace lengths to suppress EMI - incorrect placement causes excessive ripple and efficiency loss in REG71055DDCR operation.

How does REG71055DDCR behave during thermal shutdown?

When the REG71055DDCR junction temperature reaches ~160°C, internal thermal protection disables the output driver and halts switching, dropping VOUT to near zero. The device remains latched off until the die cools to ~140°C, at which point regulation resumes automatically without external reset. During shutdown, quiescent current stays at ~100 μA - not the 0.01 μA shutdown mode value - because the control circuit remains partially active. Repeated thermal cycling indicates inadequate heatsinking or excessive load; derate output current or improve PCB copper area if shutdown occurs in normal operation.