STMicroelectronics ST755CD

Overview

ST755CD from STMicroelectronics is an adjustable inverting negative-output current-mode PWM DC-DC regulator with integrated P-channel Power MOSFET, supporting 2.7V–11V input to programmable negative output (e.g., −5V), 200mA guaranteed load current (VI > 4.5V, TA ≤ 70°C), 160kHz fixed-frequency operation, and shutdown control via logic-level SHDN pin.

For engineers reviewing the ST755CD datasheet, ST755CD pinout, ST755CD application, or ST755CD equivalent, key selection criteria include negative output adjustability via external resistor divider, soft-start capability, low-noise performance, 1.2mA no-load supply current, and SO-8 thermal design constraints for industrial power conversion.

Technical Context

The ST755CD implements current-mode PWM control with internal error amplifier, 1.25V reference (VREF), and fixed 160kHz oscillator-enabling stable regulation under variable line/load conditions. Its BCD process ensures high temperature stability and low quiescent current (1.2mA active, 10µA shutdown).

It uses a 0.7Ω P-channel MOSFET switch (LX pin) and supports adjustable output via feedback resistors (R3/R4), with soft-start controlled by external capacitor on SS pin and shutdown triggered by logic-low SHDN input (<0.25V).

Key Specifications

Pinout & Package

ST755CD is housed in an SO-8 package (ECOPACK® compliant, lead-free, 1.27mm pitch), with exposed pad not electrically connected. Thermal resistance junction-to-ambient is 160°C/W under standard PCB layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar inverting negative-output DC-DC regulator applications.

Compared with LM2662CMX/NOPB and MAX765CPA+, ST755CD uniquely combines adjustable negative output, soft-start, low-noise PWM operation, and 200mA guaranteed current-making it optimal for precision analog and battery-sensitive applications where inductor use is acceptable.

Availability

ST755CD is available at Aetrix Electronics and suitable for industrial sensor conditioning, portable medical instrumentation, test & measurement equipment, and automated test equipment requiring stable component supply and long-term obsolescence management.

Supply support for ST755CD 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 microcontrollers, power ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

The ST755 series belongs to ST's legacy power management portfolio, engineered specifically for compact, efficient generation of negative supply rails in space-constrained analog systems using minimal external components.

FAQ

What is the maximum allowable input-to-output differential voltage for ST755CD?

The absolute maximum input-to-output differential voltage is limited to VCC + |VO| < 12.7V per datasheet Section 3. Exceeding this risks damage to the internal P-MOSFET and compensation circuitry. For example, at VCC = 6V, VO must remain above −6.7V (e.g., −5V is safe; −8V violates the limit). This constraint governs minimum input voltage selection when targeting deeper negative outputs.

How is output voltage adjusted on the ST755CD?

Output voltage is set by a resistor divider (R3/R4) between VO and GND, with the junction connected to VREF (Pin 2). Using the formula R4 = (|VO| / 1.25V) × R3, designers select R3 (2kΩ–20kΩ) and calculate R4 for target |VO|. For −5V output, R3 = 10kΩ yields R4 ≈ 40.7kΩ. The VREF tolerance (±5%) directly impacts output accuracy.

Can ST755CD operate from a 3.3V input to generate −3.3V?

Yes, but output current is reduced: at VCC = 3.3V and VO = −3.3V, the datasheet guarantees only 125mA (Section 4, Table 5). This stems from reduced headroom for the internal P-MOSFET and lower efficiency. For full 200mA capability, VCC must exceed 4.5V. Layout must minimize trace inductance to maintain stability at lower input voltages.

What is the purpose of the CC pin, and how is it configured?

The CC pin (Pin 4) is the compensation node for the error amplifier. It requires an external RC network (typically 7.5kΩ + 1nF) between CC and GND to stabilize the control loop. Incorrect compensation causes oscillation or poor transient response. The value is derived from the internal transconductance amplifier and external output filter characteristics, as detailed in Application Note AN2027.