Some time ago, the landlord wants to join the CC box V1.1 lithium battery, so that CC can box when there is a demand, wherever you go. Since the CC box with a TFT screen and a variety of sensors and WIFI module (if insufficient current will cause WIFI module stop restart), the landlord after preliminary statistics, current boost IC output at least 600ma or more. Then, select the boost this program lithium batteries will need extra attention. Later, an engineer friend recommended lt1308 chip to the landlord. Well, let's take a look at the introduction of this chip. Linear's LT1308 is a DC-DC boost chip, the following properties: LT1308A / LT1308B is operating input voltage range 1V to 10V in micro-power, fixed frequency step-up DC / DC converter.
1, there is provided a lithium ion battery from a single 5V 1A continuous current
2, the SEPIC continuous mode provides 5V 0.8A current from four nickel-cadmium batteries
3, Boost Frequency: 600kHz
. 4, the output voltage of up to 34V
. 5, can load high starting
6 , automatic mode is started at a low load ModeTM (LT1308A)
. 7, a light load may be continuously switch (LT1308B)
. 8, low pressure drop: 2A 300mV typ
. 9, pin-for-pin compatible upgrade LT1308
10, a low quiescent current shutdown mode: 1mA (max)
11, to improve the low battery detector accuracy: 200mV ± 2% performance parameters such a look, reckon the landlord, the landlord can exceed the requirements. So do not hesitate to choose this chip.
Due to its typical schematic Sprinter Datasheet not complete and provided, where the landlord Videos another schematic view of the connector according to the principle of this kind will be better able to run an electronic component directly. Wherein: SHDN is the start bit, it is determined that activation condition level higher than 1V, it can be directly connected to the correct input pole (below) (you can put it connected to the potentiometer, the potentiometer is connected to the input it is to change the advantage a battery (e.g., lithium) to start protection level) Further, the output current is large, the input capacitor should be as large enough, more preferably 100uF output capacitance required is large enough, but not necessarily must be greater than the input capacitance, resistance FeedBack assigned as shown below (5V may be used when the output resistance 309K, 100K), if the resistance of 309K hard to find, and a voltage less strict, the output can be used with resistor compositions 5V 10K, 3.3K, and 50K can also be used to potentiometer. FeedBack potential of 1.22V,
Output voltage equation is: VOUT = 1.22V * (1 + R18 / R19).
When using a single 1.5V alkaline or nickel electrical input, the output voltage of 5V, can provide a maximum output current is about 100mA, if the load continues to increase, the output voltage will significantly reduce the efficiency is low. When using lithium 3.7V input, output voltage 5V, a maximum output current is about 1000mA, efficiency up to 85%.
PCB layout
+ 3M thermally conductive adhesive tape on another point chip, the chip's heat is relatively large, conditions may be 8 * 8 buy aluminum fin
