LM334Z Principle
The LM334Z is a three-terminal adjustable current source. Like the LM134 and LM234, its current output is determined by an external resistor and no other external components are required. The LM334Z can provide a current output from 1 µA to 10 mA by adjusting the external resistor between the pin and the negative supply pin.
The LM334Z sets the output current by an external resistor based on its internal circuit design. For the LM134/LM234/LM334 series, the voltage on the control pin is 64mV at +25°C, which is proportional to the absolute temperature (°K). The simplest external resistor connection produces a current with a temperature dependence of approximately 0.33%/°C.
To achieve zero temperature drift, additional resistors and diodes can be added to the external circuit to compensate for the effects of temperature changes. In addition, a reverse voltage of up to 20V will only draw a few microamps of current, which allows the LM334Z to be used as a current source in AC applications and rectifier circuits.
LM334Z Pinout
LM334Z Specifications
| Parameter | Value |
| Number of Pins | 3 |
| Supply Voltage-Min | 1V |
| Forward Voltage | 40V |
| Output Impedance | 0.8 MΩ at 100 µA |
| Operating Temperature | 0°C to 70°C |
| Power Dissipation | 400 mW (at 25°C ambient temperature) |
| Operating Voltage Range | 1V to 40V |
| Package | TO-226-3, TO-92-3 (TO-226AA) |
| Adjustable Current | Set by external resistor (Rset) |
| Initial Accuracy | ±3% |
| Compliance Voltage | Up to 40V |
| Supply Current | 1 µA to 10 mA |
| Line Regulation | 0.02%/V typical |
| Load Regulation | 0.03%/V typical |
| Startup Voltage | 0.9V |
| Short-Circuit Current | Internal limiting |
| Thermal Resistance | 180°C/W (junction to ambient) |
| Noise | 100 nV/√Hz |
LM334Z Features
- The current output can be easily adjusted by an external resistor.
- Operates over a broad current range from 1 µA to 10 mA.
- Capable of operating with supply voltages as low as 1V.
- Requires minimal external components, usually just a single resistor to set the current.
LM334Z Applications
Precision Current Source: The LM334Z is used in circuits that require a stable and precise current source for adjusting the current via an external resistor.
Temperature Sensors: the LM334Z can be used in temperature sensing and compensation circuits. The voltage at the control pin varies proportionally with the absolute temperature, making it useful for thermal management systems.
Battery Chargers: It can be utilized in battery charging circuits to provide a constant current charge, ensuring the battery is charged efficiently and safely.
LED Drivers: The LM334Z can serve as an LED driver, providing a constant current to LEDs.
Analog Circuits: In analog circuits, it can be used as a reference current source.
Medical Instruments: In medical electronics, the LM334Z applies to various sensor and measurement systems.
LM334Z Manufacturer
The LM334Z is manufactured by Texas Instruments, which is known for its high-quality electronic components and has a significant presence in the global electronics market. It is a global semiconductor design and manufacturing company that develops analog ICs and embedded processors. TI is renowned for its innovation in the electronics industry and offers a broad portfolio of products that support a variety of applications in the consumer electronics, industrial, automotive, and communications sectors.
LM334Z CAD Model
LM334Z Schematic Diagram
LM334Z Package
The LM334Z is available in a TO-92 package. This package is characterized by its compact, plastic-encased form with three leads extending from the bottom, making it suitable for through-hole mounting on printed circuit boards (PCBs). The TO-92 package is widely used for low-power and small-scale electronic applications due to its ease of handling and installation.
Here are some key specifications of the TO-92 package for the LM334Z:
Lead Count: 3
Mounting Style: Through-hole
Dimensions: 4.3 mm x 4.3 mm x 5.2 mm
Weight: Approximately 0.2 grams
How To Use LM334Z?
Step 1: Connect the LM334Z's pin 1 to a positive voltage supply and pin 2 to ground, ensuring the voltage is within the operating range specified in the datasheet.
Step 2: Choose a resistor value for Rset based on the desired output current using the formula I_out = V_ref / R_set, where V_ref is approximately 64 mV for the LM334Z.
Step 3: If temperature compensation is desired, connect a resistor from pin 3 to pin 2 (ground) to adjust the temperature coefficient of the output current.
Step 4: Connect the load between pin 3 (output) and ground, ensuring the load does not exceed the maximum current specified in the datasheet.
FAQs about LM334Z
How does LM334Z work?
LM334Z operates by maintaining a constant voltage between its reference terminal (pin 2) and output terminal (pin 3). This voltage is approximately 64 mV at room temperature. By connecting an external resistor between pins 1 and 3, the LM334Z sets up a constant current determined by Ohm's law (I = V/R).
Is LM334Z sensitive to electrostatic discharge (ESD)?
Yes, like most integrated circuits, LM334Z is sensitive to electrostatic discharge (ESD). So handle the device with proper ESD precautions to prevent damage during assembly and handling.
How do I improve stability with LM334Z?
You can add a small capacitor (typically 0.1 μF to 1 μF) between pins 2 and 3, which can improve stability by filtering out high-frequency noise and improving transient response.
Conclusion
In summary, the LM334Z can easily adjust the output current through an external resistor, providing stable and precise current control for electronic designs. It is widely used in various current source applications, including bias networks, surge protection, low-power references, ramp generation, LED drivers, and temperature sensing. However, users need to pay attention to key issues such as power requirements, thermal management, and stability enhancement during use to fully utilize the performance of the LM334Z.
