Microchip TC962EPA Voltage Converter: Features and Application Circuits
The Microchip TC962EPA is a versatile and robust charge-pump voltage converter designed to provide efficient DC-DC conversion without the need for inductors. This device is capable of both voltage doubling and inverting, making it an excellent choice for a wide range of applications where space, noise, and cost are critical constraints. Its ability to deliver up to 20mA of output current from a single supply makes it suitable for powering op-amps, sensors, and other low-power circuitry.
Key Features of the TC962EPA
The standout characteristics of this IC are what make it a preferred solution for many designers.
Inductorless Operation: As a switched capacitor (charge-pump) converter, it eliminates the need for bulky and expensive inductors, simplifying board layout and reducing both EMI and overall system cost.
Wide Input Voltage Range: It operates from a supply voltage ranging from 2.5V to 12V, accommodating various power sources, including single Li-ion cells, 3.3V/5V logic supplies, and higher unregulated inputs.
High Output Current: The device can source or sink up to 20mA, which is sufficient for many analog and digital loads.
Low Quiescent Current: With a typical quiescent current of just 155µA, it is highly efficient in low-power and battery-operated devices, helping to extend battery life.
High Voltage Conversion Efficiency: It typically achieves 99% efficiency for a voltage doubler configuration, ensuring minimal power is wasted during conversion.
Simple External Components: The design requires only two flying capacitors and two storage capacitors, making the overall application circuit extremely compact and straightforward.
Application Circuits
The TC962EPA can be configured for two primary functions: voltage doubling and voltage inverting.
1. Voltage Doubler Circuit
In this configuration, the TC962EPA generates an output voltage that is approximately twice the input voltage (2 x VDD). This is ideal for generating a higher bias voltage from a low-voltage source, such as creating a +10V rail from a +5V input.
The circuit is simple:
Connect the `V+` pin to the input supply (VIN).
Connect the `C1+` and `C2+` pins to one terminal of each flying capacitor.
Connect the `C1-` and `C2-` pins to the other terminal of each flying capacitor.
The output voltage (2 x VIN) is available at the `VOUT` pin, stabilized by storage capacitors on the input and output.
2. Voltage Inverter Circuit
In this mode, the device produces a negative output voltage from a positive input, with a value of approximately -VIN. This is exceptionally useful for generating negative supply rails for operational amplifiers, analog sensors, or data acquisition systems.
The configuration is similar to the doubler but involves connecting the `V+` pin to ground and driving the `V-` pin with the input supply. The `VOUT` pin then provides the negative voltage output.
Design Considerations
Capacitor Selection: Low-ESR ceramic capacitors are highly recommended for both the flying (C1, C2) and storage (CIN, COUT) capacitors to maximize efficiency and minimize output ripple.
Output Ripple: The inherent switching action of the charge pump creates a small amount of output ripple voltage. This can be mitigated by increasing the value of the output capacitor or, in noise-sensitive applications, adding a small low-pass filter (e.g., an LC or RC filter).
Load Current: The output voltage will drop as the load current approaches the 20mA maximum. It is crucial to ensure the load requirements are within the device's capabilities for the given input voltage.
The Microchip TC962EPA stands out as an efficient and remarkably simple solution for generating secondary voltages in space-constrained, noise-sensitive, or cost-driven designs. Its inductorless architecture and minimal external component count make it a go-to IC for providing bias voltages in portable instruments, industrial sensors, and communication devices where reliability and simplicity are paramount.
Keywords: Charge-Pump Converter, Voltage Inverter, Inductorless, DC-DC Conversion, Low Quiescent Current
