ZHCSDN9A March 2015 – April 2015 ATL431 , ATL432
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 简化电路原理图
- 5 修订历史记录
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Parameter Measurement Information
- 9 Detailed Description
- 10Applications and Implementation
- 11Power Supply Recommendations
- 12Layout
- 13器件和文档支持
- 14机械、封装和可订购信息
9 Detailed Description
9.1 Overview
ATL43x is a low power counterpart to TL431 and TLV431, having lower minimum cathode current (Ik(min) = 35 µA vs 0.1/1.0 mA). Like TL431, ATL43x is used in conjunction with it's key components to behave as a single voltage reference, error amplifier, voltage clamp or comparator with integrated reference.
ATL43x can be operated and adjusted to cathode voltages from 2.5 V to 36 V, making this part optimum for a wide range of end equipments in industrial, auto, telecom & computing. In order for this device to behave as a shunt regulator or error amplifier, > 35 µA (Imin(max)) must be supplied in to the cathode pin. Under this condition, feedback can be applied from the Cathode and Ref pins to create a replica of the internal reference voltage.
Various reference voltage options can be purchased with initial tolerances (at 25°C) of 0.5% and 1.0%. These reference options are denoted by B (0.5%) and A (1.0%) after the ATL43x.
The ATL43xxI devices are characterized for operation from –40°C to 85°C, and the ATL43xxQ devices are characterized for operation from –40°C to 125°C.
9.2 Functional Block Diagram
9.3 Feature Description
ATL43x consists of an internal reference and amplifier that outputs a sink current based on the difference between the reference pin and the virtual internal pin. The sink current is produced by an internal Darlington pair.
When operated with enough voltage headroom (≥ 2.5 V) and cathode current (IKA), ATL43x forces the reference pin to 2.5 V. However, the reference pin can not be left floating, as it needs Iref ≥ 0.1 µA (please see the Functional Block Diagram). This is because the reference pin is driven into an NPN, which needs base current in order operate properly.
When feedback is applied from the Cathode and Reference pins, ATL43x behaves as a Zener diode, regulating to a constant voltage dependent on current being supplied into the cathode. This is due to the internal amplifier and reference entering the proper operating regions. The same amount of current needed in the above feedback situation must be applied to this device in open loop, servo or error amplifying implementations in order for it to be in the proper linear region giving ATL43x enough gain.
Unlike many linear regulators, ATL43x is internally compensated to be stable without an output capacitor between the cathode and anode; however, if it is desired to use an output capacitor Figure 15 through Figure 22 can be used as a guide to assist in choosing the correct capacitor to maintain stability.
9.4 Device Functional Modes
9.4.1 Open Loop (Comparator)
When the cathode/output voltage or current of ATL43x is not being fed back to the reference/input pin in any form, this device is operating in open loop. With such high gain in this configuration, ATL43x is typically used as a comparator. Due to the integrated reference, the ATL43x allows users to monitor a certain level of a single signal.
9.4.2 Closed Loop
When the cathode/output voltage or current of ATL43x is being fed back to the reference/input pin in any form, this device is operating in closed loop. The majority of applications involving ATL43x use it in this manner to regulate a fixed voltage or current. The feedback enables this device to behave as an error amplifier, computing a portion of the output voltage and adjusting it to maintain the desired regulation. This is done by relating the output voltage back to the reference pin in a manner to make it equal to the internal reference voltage, which can be accomplished via resistive or direct feedback.