“With the explosion of smart IoT devices including wireless headsets, fitness devices, smart watches, water and gas meters, portable medical devices, and various battery-powered smart IoT devices, lithium-ion battery-powered applications are becoming more and more popular. Most mobile devices need a certain constant voltage power supply to ensure the normal operation of the system. The voltage range of a lithium battery, which is generally nominally 3.7V, is 2.8V-4.2V, and the voltage decreases with the discharge. If the voltage output by the lithium battery is not suitable for the required input voltage, or the voltage variation exceeds the required tolerance range, a suitable buck-boost conversion chip is required.
With the explosion of smart IoT devices including wireless headsets, fitness devices, smart watches, water and gas meters, portable medical devices, and various battery-powered smart IoT devices, lithium-ion battery-powered applications are becoming more and more popular. Most mobile devices need a certain constant voltage power supply to ensure the normal operation of the system. The voltage range of a lithium battery, which is generally nominally 3.7V, is 2.8V-4.2V, and the voltage decreases with the discharge. If the voltage output by the lithium battery is not suitable for the required input voltage, or the voltage variation exceeds the required tolerance range, a suitable buck-boost conversion chip is required.
For example, to get a 5V voltage, a booster chip must be used. But can the two voltages of 3.3V and 3.6V be directly realized by the lithium battery through the step-down chip? Assuming that a lithium battery with a typical voltage range of 2.8V to 4.2V is to provide an output voltage of 3.3V, if a buck converter is used, the cut-off voltage of the battery must be greater than 3.3V, which cannot effectively utilize the energy stored in the battery. The buck-boost conversion chip 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, the buck-boost conversion chip can also ensure the normal operation of the load, consuming the battery stored energy to the greatest extent. electrical energy. As shown below:
A second common use for a buck-boost converter is as a voltage regulator. If there is a change in the power rail (eg 3.3V ± 10% variation) and the load requires a more precise regulation voltage (eg 3.3V ± 5% tolerance), then a buck-boost converter that can regulate the voltage is required . If components are sensitive to supply voltages (such as transimpedance amplifiers in optical modules); if other DC/DC pre-regulators are not tightly regulated in industrial applications; or if other components in the power path (such as electrical fuses, load switches, or long cables) as the current varies, the voltage may need to be more tightly regulated. This problem cannot be solved with a boost converter or a buck converter alone. However, buck-boost converters are able to regulate changing input voltages to the tighter limits required.
There are other applications where it is very convenient to choose a buck-boost converter chip. It is the automatic switching of the uninterruptible power supply. For example, a device such as a special occasion monitor is powered by a 5V USB wall adapter or two AA main batteries, and the battery voltage can vary from 3V (when the battery is new) to 1.8 V (when the battery is depleted). Only a buck-boost converter chip can handle a wide input voltage range from 5V (wall adapter) to 1.8V (no wall adapter connected and the battery is dead) and still produce a regulated 3.3V power output for the system. In addition to the buck-boost conversion chip, only two external diodes are required to avoid cross current from the wall adapter to the battery, and to seamlessly switch to battery power when the wall adapter is unplugged, the load is uninterrupted and stable. .
Shenzhen Yongfukang Technology Co., Ltd. is now vigorously promoting a DC-DC booster with 8uA ultra-low quiescent current and 600mA output for the application needs of mobile devices powered by single-cell lithium battery, lithium iron phosphate battery and 2-3 dry batteries. Step-down IC-CS5517T, dedicated to portable Electronic products. The device supports 1.8V to 5.0V battery power supply, the adjustable output voltage range is 1.2V to 5.0V, and the maximum output current can reach 500mA; because the voltage will drop as the battery discharges, using this chip can improve the battery The efficiency of the battery can be squeezed out as much as possible, which can prolong the battery life of smart IoT devices powered by button batteries, lithium batteries and multi-series alkaline battery packs.
CS5517T is an ultra-miniature, ultra-low power consumption, high-efficiency, buck-boost integrated DC-DC regulator. It is suitable for dual-cell, three-cell dry battery or single-cell lithium battery application scenarios. It can effectively extend the battery life. . CS5517T consists of modules such as current mode PWM control loop, error amplifier, comparator and power switch. The chip can work efficiently and stably in a wide load range. The CS5517T has an input voltage of 1.8V to 5.0V and provides an adjustable output voltage (1.2V to 5V). In the case of output voltage of 3.3V, input from 2.7V to 4.4V, it can provide a maximum current load of 600mA. CS5517T can set the output voltage by adjusting two external resistors. CS5517T provides a small DFN2X2_8L package for customers to choose from, and its rated operating temperature range is -40 ℃ to 85 ℃.
• High efficiency: the maximum efficiency can reach 95%
• Maximum current output capability: 0.6A
• Low power consumption: 8uA quiescent current
• Input voltage range: 1.8~5V
• Output voltage range: 1.2~5V
• Switching frequency: 1M
• Reference voltage: 0.6V
• Soft start
• Low voltage operation up to 100% duty cycle
• PWM/PFM automatic switching duty cycle is automatically adjustable to maintain high efficiency and low ripple in a wide load range
Wireless headsets, fitness devices, smart watches, water and gas meters, portable medical devices, and a variety of battery-powered smart IoT devices
CS5517T Typical Output Value Application Parameters
CS5517T Application Information
(1). CS5517T pin map and pin description
(2). Schematic diagram of CS5517T DEMO board
(3). CS5517T DEMO board PCB top-level design
(4). CS5517T DEMO board PCB bottom layer design
(5). CS5517T DEMO board patch diagram
(6). CS5517T DEMO Board Bill of Materials
(7). CS5517T DEMO board 3D layout front view
(8). The reverse side of CS5517T DEMO board 3D layout
(9). Physical drawing of CS5517T DEMO board