Voltage adjustment device MIC5236 with extremely small quiescent current and its application

    Abstract: Abstract: The MIC5236 series of devices is a DC voltage adjustment device just launched by Micrel in 2000. It has extremely low quiescent current and a wide input voltage range. It has on-chip current limiting, overvoltage shutdown and thermal shutdown functions. It can For short circuit protection and wire cell reverse polarity protection, this article introduces the performance, characteristics and internal structure of the MIC5236 series devices, and gives its typical application circuit.

    Keywords: power device voltage regulator reverse protection MIC5236

1 Overview

    The MIC5236 series device is a voltage regulator with extremely low quiescent current just launched by Micrel in March 2000. When the input voltage is as high as 30V, its quiescent current is only 20μA, making it an ideal power supply voltage regulator for high-voltage battery power supply systems. device. The MIC5236's output current is 150mA, while its reduced shutdown voltage is only 300mV. And it can withstand the impact of -20~+60V instantaneous input voltage. Like other μCap LDO devices, the connection method of MCI5236 is also very simple. The user only needs to connect a ceramic or tantalum capacitor to the input end of the device and a small 1μF capacitor to the output end to obtain a very stable output. Voltage. The MIC5236 has a logic-level compatible enable input that can be used for voltage fault indication. Additionally, the device features current limit, overvoltage, and thermal shutdown. It can effectively protect the device when the load is open circuit, short circuit and the battery polarity is reversed.

    The MIC5236 series devices have four output voltages of 2.5V, 3.0V, 3.3V and 5.0. Each output voltage has two different packaging forms. Therefore, the MIC5236 series devices have a total of 8 models. Table 1 lists these 8 models. models with different output voltages and packaging styles.

Table 1 Device models of MIC5236 series

    The main features of MIC5236 are as follows:

    ●Extremely low quiescent current;

    ●Wide input voltage range;

    ●The drop-off shutdown voltage is low, 230mV at 50mA output current; 300mV at 150mA output current;

    ●Has five voltage outputs: 2.5V, 3.0V, 23.3V and 5.0V;

    ●The stable output voltage accuracy is 1%;

    ●The use of ceramic or tantalum capacitors can make the output more stable;

    ●Can withstand -20~+60V instantaneous input voltage impact;

    ●Has input enable fully compatible with logic levels;

    ●With low voltage output indication;

    ●With over-current protection and thermal shutdown functions;

    ●With current reverse protection and battery reverse polarity protection functions;

    ●Adopts high-voltage 8-pin SOIC and 8-pin MSOP packaging forms.

2 Functions, parameters and principles

2.1 Pin function

    The pin arrangement of MIC5236 is shown in Figure 1. The following is the function description of each pin.

    ERR (pin 1): Failure output terminal. When the output voltage at the OUT terminal drops by 5% or more from its nominal output, the ERR terminal opens.

    IN (pin 2): power supply voltage input terminal. If necessary, a small surface-mount ceramic capacitor can be connected here for bypassing. This is especially important when the input voltage quality is not high or when it is not battery powered. If the ripple of the input voltage is large, a capacitor with a larger capacity can be selected.

    OUT (pin 3): standard voltage output pin.

    EN (pin 4): enable input. When this pin is low, the quiescent current of the device can be reduced to less than 0.1μA; when the input voltage is 2V, the maximum bias current of MIC5236 is 2μA. Connecting an upper resistor between the EN terminal and VIN can make EN terminal maintains an enable input voltage of 2V.

    GND (pins 5 to 8): ground pin.

2.2 Electrical parameters

    It should be noted that the device may be damaged when exposed to extreme parameters for a long time. The following are the limit parameters of MIC5236:

    ●Maximum input voltage: -20V～+60V;

    ●Junction temperature: +150℃;

    ●Storage temperature: +65℃～+150℃;

    ●Welding temperature: (5s) 260℃

    The normal operating parameters of MIC5236 are as follows:

    ●Input voltage: +2.3V～+30V;

    ●Operating temperature range: -40℃～+85℃;

    ●Junction temperature: -40℃～+125℃;

    ●Thermal resistance: MSOP package: 80℃/W;

    When packaged in SOIC: 63℃/W.

2.3 Working principle

    MIC5236 contains a differential amplifier and comparator, and the internal reference voltage source provides reference input signals for the differential amplifier and comparator. The internal principle of MIC5236 is shown in Figure 2. When the OUT terminal of the device outputs a normal operating voltage, the non-inverting input of the on-chip comparator taken from the OUT terminal reaches a differential balance with the inverting input provided by the on-chip reference source. Therefore, the output of the ERR terminal is zero. However, if an overload occurs and the output current increases (exceeds the current threshold), the input voltage is too low, or the on-chip temperature is too high, the device will enable the EN terminal and react at the OUT terminal to cause the output voltage to change. , thereby breaking the input balance of the comparator and making it have a certain output.

3 Typical applications

    The MIC5236 series voltage regulation devices are widely used in power systems of notebook computers and portable personal computers, automotive electronics, battery power systems, and high-voltage batteries that require high-voltage batteries to provide logic levels due to their extremely low quiescent current and wide input voltage range. Signal application system. Figure 3 is a typical application circuit of MIC5236.

    In Figure 3, a 200kΩ resistor REN is connected between the input terminal and the EN terminal to maintain the enable voltage of 2.0V at the EN terminal to ensure that the device can survive abnormal conditions such as overload, input overvoltage or excessive temperature in the system. effectively control the device. The main task of the 200kΩ feedback resistor Rf at the input end and ERR end is to avoid output oscillation and eliminate slow changes from low voltage to high voltage. The function of the diode is to make the MIC5236's control of the system more reliable.

    If the input voltage is not provided by a battery, or the quality of the input voltage is not high, a bypass capacitor should be connected to the input terminal. Tantalum capacitors or small SMT ceramic capacitors can be used. If the ripple of the input voltage is large, bypass The capacity of the capacitor can be larger.

    Since MIC5236 has adopted a unique design internally, the output capacitor COUT only needs a general 1μF film or ceramic capacitor to ensure the stability of the output.