Specifications

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5.2.1 Verifying Power Hardware
Since excessive voltages can damage the integrated circuits, it is necessary to
test the voltage regulators and battery first. To do this, a multimeter will be used.
The battery can be tested by measuring the voltage across the positive and
negative terminals using a multimeter. It is not necessary to connect the battery
into a circuit. The voltage must be verified to be close to 7.4Vdc. If this is not the
case, ensure the battery is fully charged, and then try again.
For the voltage regulators, a basic circuit must be established. Using the
schematics available in the voltage regulators section, connect each voltage
regulator in a separate circuit utilizing filtering capacitors, and positive and
negative connections. Common connections should be grounded. In addition, a
heatsink is recommended for the 5Vdc regulator. The 12Vdc external source
should be connected to both units. Both units should have a parallel
configuration. At this point, connect the positive lead of the multimeter to the
output of the 5Vdc regulator. Connect the common lead to ground of the circuit.
Verify that the output voltage is a nominal 5Vdc. If not, disconnect the 12Vdc
source and measure it with respect to ground. Ensure the source is correct. If
correct, ensure there is no short circuit present. Repeat the procedure for the
3.3Vdc regulator.
One question is that of the value of the Rsense resistor in the circuit of the
charging IC. This resistor determines the charge current, and thus, the charge
time and speed of the battery. There are several considerations to be made in
choosing this value. First is the issue of heat. While the IC can dissipate large
amounts of heat through its integrated thermal pad (and thus use the copper
ground plane as a large heatsink), the other components may not be able to. As
such, an appropriate charge current is needed. In addition, while the IC can
handle large amounts of heat, it can only handle a certain amount before
reaching an auto-shutdown state. This state was encountered several times in
testing. To determine an optimal resistance, several trials were conducted to
determine which Rsense value should be used. The results are summarized in
Table 5.2.1-1.