How to Select IC Power Supplies
Image Credits: Allied Electronics, Newark, and ROHM Semiconductor
Integrated circuit (IC) power supplies receive an unregulated input and provide a regulated output voltage.
How IC Power Supplies Work
IC power supplies take unregulated input, change and/or regulate it to another voltage level, and output the adjusted power. Using a regulated IC power supply ensures the safety and efficient use of circuitry that requires a narrow voltage range. This video illustrates.
Video Credit: Element 14/Freescale Semiconductor
Types of IC Power Supplies
IC power supplies generally are linear regulators, switching regulators, and charge pumps.
- A linear regulator steps down input voltage to a lower level. They are small and relatively inexpensive. Common topologies are standard (NPN Darlington), low drop out (LDO), or quasi-LDO.
- Switching regulators step down (buck), step up (boost), or invert (buck-boost) the polarity of the incoming voltage. They tend to be larger and more expensive.
- Charge pumps act like switching regulators, but only at a limited load current. They can output either regulated or unregulated voltages.
Other devices include CUK, flyback, and forward converters.
Important specifications when selecting IC power supplies include,
- Input voltage (VIN) ranges (e.g., 0.95 to 14 volts).
- Output voltage (Volt) can be fixed (e.g., 4 or 12 VDC) or adjustable, regulated or unregulated, same or opposite polarity. Output has a tolerance (a guarantee that it will remain within a certain range).
- Output current (Iout) ranges (e.g., 0.017 to 5 amps).
- Quiescent (operating or ground) current (IQ) powers the regulator itself and ranges (e.g., 0.00014 to 0.85 amps).
- The devices are designed to operate in a certain temperature range (e.g., -40 to 85 C).
For switch types, switching frequency (fsw) ranges (e.g., 112 kHz to 96 mHz), efficiency (through the duty cycle) can be at least a certain percentage (e.g., 74, 87).
IC power supplies feature several main characteristics such as,
- Shutdown (inhibit) pins disable the output.
- Protective measures guard against reverse voltage, input overcurrent, or over heating (thermal shutdown)
- An error flag alerts when output has dropped (generally 5%) below its nominal value.
- One or multiple outputs exist.
- Synchronous rectification contrasts with diode rectification.
IC power supplies are found in computing, medical, military, telecommunications, and industrial equipment; indeed, anywhere a circuit board is used.