LM723
LM723/LM723C Voltage Regulator Technical Summary
Overview
The LM723/LM723C is a highly versatile voltage regulator IC designed primarily for series regulator applications. This component serves as a fundamental building block in power supply circuits, offering flexibility through external component configurations. With its built-in reference voltage and error amplifier, the LM723 provides precise voltage regulation while supporting a wide range of output current capabilities through the addition of external pass transistors.
Originally developed by National Semiconductor (now part of Texas Instruments), the LM723 has become an industry-standard regulator IC due to its reliability and adaptability. The device operates over a wide input voltage range and maintains excellent regulation characteristics, making it suitable for both simple and complex power supply designs.
Key Features
- Wide Input Voltage Range: Operates from 9.5V to 40V input voltage
- Built-in Reference Voltage: Features a stable 7.15V reference with ±1% tolerance
- Adjustable Output Voltage: Configurable from 2V to 37V
- Current Limiting Capability: Supports both linear and foldback current limiting
- Low Standby Current: Typically draws only 2.5mA when idle
- High Current Capability: 150mA output current without external pass transistor
- Expandable Current: Output currents exceeding 10A possible with external transistors
- Thermal Protection: Built-in thermal shutdown protection
- Operating Temperature Range: 0°C to +70°C for LM723C, -55°C to +125°C for LM723
Applications
The LM723 finds application in numerous power regulation scenarios due to its flexible architecture:
Primary Applications
- Series voltage regulators
- Adjustable power supplies
- Laboratory power supplies
- Battery chargers
Secondary Applications
- Shunt regulators
- Current regulators
- Switching regulators
- Voltage monitoring circuits
- Over-voltage protection circuits
Electrical Characteristics
Absolute Maximum Ratings
- Input Voltage (V+ to V-): 40V
- Power Dissipation: 800mW
- Output Current (Internal): 150mA
- Storage Temperature Range: -65°C to +150°C
- Junction Temperature: 150°C
Typical Operating Characteristics (TA = 25°C)
| Parameter | Conditions | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Reference Voltage | Iref = 0mA | 7.08 | 7.15 | 7.22 | V |
| Input Voltage Range | 9.5 | - | 40 | V | |
| Output Voltage Range | 2 | - | 37 | V | |
| Line Regulation | V+ = 12V to 40V | - | 0.01 | 0.1 | %/V |
| Load Regulation | IL = 0 to 50mA | - | 0.04 | 0.3 | % |
| Standby Current | V+ = 40V, No Load | - | 2.5 | 3.5 | mA |
Package Information
Available Packages
- 14-Pin PDIP (N): Plastic Dual In-Line Package
- 14-Pin SOIC (D): Small Outline Integrated Circuit
- 10-Pin TO-100 (H): Metal Can Package
Pin Configuration (14-Pin PDIP)
| Pin Number | Symbol | Function |
|---|---|---|
| 1 | NC | Not Connected |
| 2 | CL | Current Limit |
| 3 | CS | Current Sense |
| 4 | IN- | Inverting Input |
| 5 | IN+ | Non-inverting Input |
| 6 | Vref | Reference Voltage Output |
| 7 | V- | Negative Supply |
| 8 | NC | Not Connected |
| 9 | Vz | Zener Diode Anode |
| 10 | Vout | Regulator Output |
| 11 | Vc | Collector of Pass Transistor |
| 12 | V+ | Positive Supply |
| 13 | NC | Not Connected |
| 14 | NC | Not Connected |
Design Considerations
Current Limiting
The LM723 offers two methods of current limiting:
- Linear Current Limiting: Provides constant current when limit is reached
- Foldback Current Limiting: Reduces current as output voltage decreases during overload
Thermal Considerations
When designing with the LM723:
- Ensure proper heat sinking for high current applications
- Keep trace lengths short for current sense connections
- Use proper decoupling capacitors near supply pins
- Consider derating specifications for elevated temperature operation
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