usb power and charger circuit design question

iam trying to follow this Sparkfun project example
I will be powering the circuit by a 3.7v single cell Lipo battery with built in protection board. Also I will be using the usb power to charge the battery when usb is plugged in.
I have few questions though:

1) in the first diagram picture I am not sure what they mean by "Vin must be 4.5-5.5 v when battery charger is used" ?
since I wont be using any external power other than usb can I remove the circuit components in the upper red box ?

2) also in the first diagram since I will not be using the USB host enable feature so can I remove the components in the lower red box ?

3) I am not understand the functions of the jumpers in the second diagram for battery charge circuit.

in summary how can I modify this circuit to be able to use usb to give 3.3v and also charge the battery at the same time when plugged and have the battery supply the 3.3v when the usb is unplugged?

thanks

Hi

1. You can remove external source circuit if you d'not need. circuit design for 4.5 to 5.5v DC.
2. Yes...you can remove red mark area circuit and Q1 & R5 also.
3. Jumper is connecting R1 to MCP73831 output current limit pin. It uses for battery fast & low charging. Preconditioning, fast charge and termination currents
are scaled by placing a resistor from PROG to VSS.

You should use always battery power for your circuit.

Ranbeer Singh said:

Hi

3. Jumper is connecting R1 to MCP73831 output current limit pin. It uses for battery fast & low charging. Preconditioning, fast charge and termination currents
are scaled by placing a resistor from PROG to VSS.

You should use always battery power for your circuit.

Click to expand...

hi Ranbeer
iam talking about jumpers JP4,JP8 and JP9 , what are their functions ? should I use them?
also the Lipo batteries I will be using have built in charge protection circuit so would I still need this charge control circuit ?

jp4, jp5 & jp9 are not jumpers.... These are connector for carry the battery voltage out for use. D,not short them otherwise your battery will be short circuitous.

I have more questions related to this circuit and in general .
how is this circuit working , when the usb is attached , is the usb power charging the battery and also supplying power to the circuit board or is the power supplied to the circuit board is only by battery and the usb power is only delivered to charging the battery ?

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please take a look at the circuit below , can you point out whats the best recommended way of connecting the battery in this case ?

It is asking a lot, to expect a reader to know how the IC works, and how to combine functions, and to know how your equipment works.

Many functions need to be performed in this project: (a) charging with load, (b) charging without load, (c) supplying a load. You'll need to test each function individually, to make certain equipment cooperates. Then eventually you might combine all functions. Even then it will require more experimentation, to get them to be compatible. You may need to consider maximum capabilities of USB power. You may need to install protection for expensive devices.

The best way to get answers to many of your questions, is by hooking up components, and experimenting on your own. Find out about what caution you need to exercise when hooking up a Li battery, if you aren't sure about the circuitry misbehaving. Expect to burn up a few devices. That is frequently the price of making a project that saves you money.