Technical Information Paper A NEW METHOD,PARALLEL TWO SUPPLIES
●This new document will present a way to parallel two supplies (the main board supply and a Li-Ion battery) in order to power a single output. While the Li-Ion battery is not in use, it will get recharged by sampling a small portion of the current from the main board supply. The reader is advised to review TIP No.28 before going any further, because this new document further expands on the concept introduced in TIP No.28. Please note that the only IC that should be recommended with this new circuit configuration is the XC9135M (Output voltage internally set, no CL discharge function, UVLO –Under Voltage Lock Out- threshold can be factory-set up to 3.0V).
●The below circuit diagram shows the proposed solution. As you can see, the input power is split between the XC6227 LDO voltage regulator (with built-in reverse current protection) and the XC6802 Li-Ion battery charger. A XC9135M synchronous step-up DC/DC converter is connected after the Li-Ion battery, and the XC9135M output is paralleled with the XC6227 output. The XC6227, XC6802 and XC9135M are all Torex ICʼs. As detailed within TIP No.28, the MODE pin of the XC9135M must be set to ʻLowʼ.
●You may have noticed that the EN and BAT pins of the XC9135M are connected together. This permits the circuit to still supply current to its output even after the main board supply is disconnected, without requiring an additional logic signal to control the EN pin. But the compromise is that the XC9135M will only stop operating when its UVLO function detects that the Li-Ion battery voltage is too low. If you want to keep more control over the enabling/disabling of the XC9135M (especially when the main board supply is disconnected), and if you can afford to use one additional logic signal, this signal can control the EN pin of the XC9135M.
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Datasheet |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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2015 |
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344 KB |
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