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ua723cn-voltage-regulator

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Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

UA723CN - Precision Adjustable Linear Voltage Regulator

Details

Description

The UA723CN is a precision integrated-circuit voltage regulator featuring high ripple rejection, excellent input and load regulation, excellent temperature stability, and low standby current. The circuit consists of a temperature-compensated reference voltage amplifier, an error amplifier, a 150mA output transistor, and an adjustable-output current limiter. This classic IC can be configured for use in positive or negative power supplies as a series, shunt, switching, or floating regulator, making it extremely versatile for various power supply applications.

Specifications

Electrical Characteristics

  • Input Voltage: Up to 40V maximum
  • Output Voltage: Adjustable from 2V to 37V
  • Output Current: 150mA maximum (without external pass transistor)
  • Load Regulation: Excellent (typically <0.1%)
  • Line Regulation: Excellent (typically <0.01%/V)
  • Temperature Coefficient: Low (typically 0.002%/°C)
  • Ripple Rejection: High (typically 74dB)
  • Standby Current: Low power consumption

Physical Characteristics

  • Package: 14-pin DIP (Dual In-line Package)
  • Dimensions: 0.300” (7.62mm) width
  • Pin Pitch: 0.100” (2.54mm)
  • Operating Temperature: 0°C to +70°C

Key Features

  • Precision voltage regulation with excellent stability
  • Adjustable current limiting capability
  • High ripple rejection and low noise
  • Temperature-compensated reference voltage
  • Can be used in various regulator configurations
  • External pass transistor capability for higher currents

Pinout Diagram

    UA723CN 14-Pin DIP
    ┌─────────────────┐
NC  │1             14│ NC
CUR │2             13│ COMP
CUR │3             12│ VC
INV │4             11│ VC+
REF │5             10│ VOUT
NON │6              9│ V+
V-  │7              8│ VREF
    └─────────────────┘

Pin Descriptions

PinNameDescription
1NCNo Connection
2CURCurrent Limit (sense resistor connection)
3CURCurrent Limit (sense resistor connection)
4INVInverting input of error amplifier
5REFReference voltage output (~7.15V)
6NONNon-inverting input of error amplifier
7V-Negative supply (ground in positive supplies)
8VREFReference voltage input
9V+Positive input voltage
10VOUTRegulated output voltage
11VC+Collector of output transistor
12VCCollector of output transistor
13COMPFrequency compensation
14NCNo Connection

Applications

Common use cases for the UA723CN:

  • Adjustable bench power supplies
  • Precision voltage references
  • Battery chargers with voltage regulation
  • Laboratory and test equipment power supplies
  • Current-limited power supplies
  • Positive and negative voltage regulators
  • Switching regulator control circuits
  • High-precision analog circuit power supplies

Circuit Examples

Basic Positive Voltage Regulator (5V Output)

Input (9-40V) ---- V+ (Pin 9)
Ground ---- V- (Pin 7)
VREF (Pin 8) ---- REF (Pin 5) via 2.2kΩ resistor
VOUT (Pin 10) ---- Output (5V)
Voltage divider: VOUT ---- 2.4kΩ ---- INV (Pin 4) ---- 3.9kΩ ---- Ground
NON (Pin 6) ---- VREF (Pin 8)
VC+ (Pin 11) ---- VC (Pin 12) ---- V+ (Pin 9)
COMP (Pin 13) ---- 100pF capacitor ---- INV (Pin 4)

Current Limited Supply

Standard regulator circuit plus:
Current sense resistor (0.6Ω) between VOUT and load
CUR pins (2,3) connected across sense resistor
Provides ~1A current limiting

High Current Regulator (with external pass transistor)

External NPN power transistor:
Base ---- VOUT (Pin 10)
Collector ---- Input voltage
Emitter ---- Regulated output
UA723 provides control, external transistor handles current

Programming/Control Examples

Variable Output Voltage

Use potentiometer in voltage divider:
VOUT ---- Fixed resistor ---- Potentiometer ---- Ground
Wiper of potentiometer ---- INV (Pin 4)
Allows continuous adjustment of output voltage

Precision Current Source

Configure as current regulator:
Reference voltage across precision resistor
Provides constant current output
Useful for LED drivers and battery charging

Technical Notes

Important considerations for the UA723CN:

  • Heat Dissipation: Use adequate heat sinking for high power applications
  • Stability: Frequency compensation may be needed for some configurations
  • Current Limiting: Built-in current limiting protects against overload
  • External Pass Transistor: Required for currents >150mA
  • Precision: Excellent regulation makes it suitable for precision applications
  • Versatility: Can be configured in many different regulator topologies

Design Calculations

Output Voltage Setting

VOUT = VREF × (1 + R1/R2)
Where:
- VREF ≈ 7.15V (internal reference)
- R1 = feedback resistor from output to INV pin
- R2 = resistor from INV pin to ground

Current Limiting

ILIMIT = 0.6V / RSENSE
Where:
- 0.6V is the voltage across current limit pins
- RSENSE is the current sense resistor value

Tags

voltage-regulator, linear-regulator, adjustable-regulator, precision-regulator, texas-instruments cabinet-3 bin-33 status-available

Notes

The UA723CN is a classic and highly versatile voltage regulator IC that has been a staple in power supply design for decades. Having this component in your collection provides access to precision voltage regulation with excellent stability and flexibility. It’s perfect for building custom power supplies, voltage references, and current-limited supplies. The ability to configure it in various topologies (series, shunt, switching, floating) makes it invaluable for both learning power supply design principles and for practical applications. Despite being an older design, it remains relevant due to its precision, stability, and proven reliability. This IC is excellent for educational projects, precision analog circuits, and anywhere adjustable, stable voltage regulation is needed.

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