500NA Power Monitor extended the life of lithium battery in portable applications (08-100)

　　Author ：Iflowpower – Portable Power Station Supplier

Introduction In the design of electronic devices (especially battery-powered products), power consumption is an important issue. With regard to electronic equipment designers, the face-to-face problem is how to add functions without significantly shortening equipment battery run. For example: Unpacking any stylish portable device, you will find that many integrated circuits will consume certain current even when they are in idle state.

The static current and operating current of the embedded circuit should be reduced as much as possible (in order to maximize the life of the battery), this is important. Sometimes, under weak battery voltage conditions, when you turn on your device, you may only find that it does not have any reaction, and is partially configured after it is terminated prematurely. One way to prevent this problem is to monitor the power source monitor with extremely low power demand to monitor the system power supply, so that they can respond even in the case where the battery is consumed very much.

The LTC2934 and LTC2935 ultra-low power monitors provide accurate voltage monitoring and microprocessor control during all phase of the equipment. System initialization, power failure warning, manual reset, and power-on / power-down reset occurrence function are built into the device, and thus only the current from the power absorption zone 500na is required. While it is very suitable for battery-powered products, the LTC2934 and LTC2935 can also be used in applications where the voltage monitoring and / or microprocessor control is controlled.

The ultra-low load current of these surveillars makes the product capable of using a small capacity, and has a longer working time. Its typical application includes portable data logger, medical equipment, remote systems, and essential security equipment. Figure 1 Typical power monitor application power supply voltage rises: Starting is important to control the launch of devices during power-on-power-powered, this is important.

The LTC2934 / 35 power-on (POR) function is supplied to voltage monitoring and logic control, which is used to prevent the microprocessor in the case of insufficient power supply voltage. The PRO function also has a delay, so that the stable supply of the power supply voltage supply a little margin. This delay also enables a processor oscillator to enable a stable frequency before allowing the microprocessor to perform encoding operations.

Reset Output / RST from the monitor is usually connected to the reset input of the microprocessor. During the system startup, the monitor holds the / RST output at a low level. When the voltage reaches a specified minimum, the internal reset press will start running, and the / RST output is maintained at a low time (usually 200 ms).

When the reset press is terminated, the / RST output is pulled to a high level and releases the microprocessor from its reset state. Figure 2 shows the power supply rising waveform obtained from the typical application circuit shown in Figure 1. When VCC exceeds the power failure threshold 2.

5% hysteresis (3.192VX1.025 = 3.

272V), the power failure output (/ PFO) is allowed to pull to a high level. LT3009 (a 3Aldo) is powered from VCC. Since the / PFO output is pulled up from the LDO output, / PFO will follow LDO.

When the LDO output exceeds the reset threshold 5% hysteresis (1.696VX1.05 = 1.

781V), the internal reset press starts running. After 200 ms, / RST is pulled to a high level, and the system logic circuit connected to / RST is released from its reset state. Figure 2 Typical power-up waveform power supply voltage drop: Note that the warning non-controlled power loss will cause many system problems.

The LTC2934 and LTC2935 include a power failure logic output (/ PFO) that pulls it to a low level to lose the warning of the upcoming power supply. The alarm should be supplied before the voltage of the monitored power supply is lowered (and when it is long as the / RST output is pulled to a low level), so that utility can be used. The time between PFO and / RST is pulled to a low level can be used to start a number of key operations before stopping.

When the monitor pulls the microprocessor to the low level, it may not be possible. The operation initiated by the power failure alarm signal includes: shutting off the non-critical element (in saving energy) and writes important data to the memory. Some security applications may also require data to delete data, so that the memory is not allowed to make a machine.