How to realize the stable output of 3.3v/3.6v (1.2-5v) voltage of lithium battery by using the voltage rise and fall chip cs5517

With Including wireless headphones 、 Fitness equipment 、 Intelligent Watch 、 Water and gas meters 、 Portable medical devices and various battery powered intelligent IOT devices The explosive growth of , The application of lithium battery as power supply is becoming more and more popular . Most mobile devices require a certain amount of Constant voltage power supply , To ensure the normal operation of the system . Generally, the nominal value is 3.7V The voltage range of the lithium battery is 2.8V-4.2V, As the discharge voltage drops . If the output voltage of the lithium battery is not suitable for the required input voltage , Or the voltage variation exceeds the required tolerance range , be Appropriate voltage conversion chips are required .

  For example, to get 5V voltage , We have to use a boost chip . but 3.3V、3.6V Two voltages , Can it be realized directly by the lithium battery through the step-down chip ？ Suppose that a typical voltage range is 2.8V To 4.2V The lithium battery provides 3.3V The output voltage of , If a step-down converter is used , Then the cut-off voltage of the battery must be greater than 3.3V, Unable to effectively use the electric energy stored in the battery . and step-down - The boost converter helps to make full use of all the power of the battery , Because when the input voltage is equal to or lower than 3.3V when , step-down - The boost converter can also consume the stored electric energy .

 

  step-down - The second common use of boost converters is as voltage regulators . If the power rail changes （ Such as 3.3V±10% change ）, The load needs to adjust the voltage more accurately （ Such as 3.3V±5% tolerance ） when , Then you need a step-down that can stabilize the voltage - Boost Converter . If the component is sensitive to the supply voltage （ For example, transimpedance amplifier in optical module ）; If other DC/DC The pre regulator is not tightly regulated in industrial applications ; Or if other components in the power path （ Such as electric fuse 、 Load switch or long cable ） Increase according to current change , It may be necessary to regulate the voltage more strictly . Only the step-up converter or step-down converter can not solve this problem . However , step-down - The boost converter can adjust the changing input voltage to the required stricter limit .

 

  There are other reasons to choose to reduce blood pressure - Boost Converter , Instead of simply choosing a step-down converter or a step-up converter . One reason is power ORing. Imagine a device like a baby monitor , It consists of a 5V Of USB Wall adapter or two pieces AA Main battery power supply , The voltage variation range is 3V（ When the battery is new ） to 1.8 V（ When the battery runs out ）. Only depressurization - The boost converter can withstand from 5V（ Wall adapter ） To 1.8V（ The wall adapter is not connected and the battery is exhausted ） Wide input voltage range , And still generate for the system 3.3V Power rail . Except Depressurization - Boost Converter , You just need Two external diodes This avoids cross currents from the wall adapter to the battery , And seamlessly switch to the battery when pulling out the wall adapter .

 

  Shenzhen yongfukang Technology Co., Ltd. aims at single lithium battery 、 Lithium iron phosphate battery and 2-3 Demand for mobile devices powered by dry batteries , Now vigorously promote one with 8uA Ultra low quiescent current 、600mA Output DC-DC Pressure rise and fall IC-CS5517T, For portable electronic products . The device Support 1.8V to 5.0V Battery powered , Adjustable output voltage range 1.2V to 5.0V, The maximum output current can reach 500mA; Because as the battery discharges , The voltage will drop , Using this chip , Can improve the efficiency of the battery , Drain the battery as much as possible , Extendable button battery 、 Battery life of intelligent Internet of things devices powered by lithium battery and multi series alkaline battery pack .

 

 

Summary

CS5517T It's a super micro 、 Ultra-low power consumption , high efficiency , Integrated lifting and pressing DC-DC an adjuster . Applicable to two sections , Application scenarios of three dry batteries or single lithium battery . It can effectively prolong the service time of the battery .CS5517T By the current mode PWM Control loop , Error amplifier , Comparator, power switch and other modules . The chip can work efficiently and stably in a wide load range .CS5517T The input voltage of is 1.8V to 5.0V Provide adjustable output voltage of (1.2V to 5V). When the output voltage is 3.3V Under the circumstances , Input from 2.7V To 4.4V, It can provide maximum 600mA Current load . CS5517T The output voltage can be set by adjusting the two external resistors .CS5517T Provides a slim DFN2X2_8L Package form Customers can choose , Its rated operating temperature range is -40℃ to 85℃.

characteristic

high efficiency ： Maximum efficiency can be achieved 95%

Maximum current output capability ：0.6A

low power consumption : Quiescent current 8uA

Input voltage range ：1.8~5V

Output voltage range ：1.2~5V

Switching frequency :1M

Reference voltage ：0.6V

Soft start

Low voltage operation , Can be up to 100% Duty cycle

PWM/PFM Automatic switching duty cycle is automatically adjustable to maintain high efficiency over a wide load range , Low ripple

application

Wireless headset 、 Fitness equipment 、 Intelligent Watch 、 Water and gas meters 、 Portable medical devices and various battery powered intelligent IOT devices

Pin arrangement and definition

Typical application diagram