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Test Summary

4.3 Test Procedure

1. Make sure that the EVM is set up according to Table 1 and Figure 1, and the power supply is preset to

5.1 VDC at ~1250 mA current limit.

2. Turn on input supply and verify the power supply current meter is between 0.26 A and 0.31 A. Note

that this is a linear charger so the input current is approximately the output current minus any current

going to VLDO. The battery voltage, DMM#1, should have increased slightly (few mV) due to the IR

drop in the battery (I

OUT

times mΩ of the cell).

3. Verify that the IMON pin is between 270 mV and 310 mV, DMM#3. The IMON output current is 1/1000

of the OUT current and is converted to a voltage using a 1k IMON resistor (1 V/1 A).

4. Verify that the CHG LED is lit.

5. Program the charger for ~0.95 A by placing a shunt on JP-111 (11 pulses - only one shunt on the

JP1xx connectors at the bottom of the EVM) and toggling S100 From: Down TO: Up To: Down

position.

6. Verify the power supply input current is between 0.93 and 0.98A. If current does not change, verify that

the 11 pulses were generated and the pulse frequency is ~500 Hz, 50% duty cycle (see data sheet

specification for further details). R106 can be adjusted to vary frequency (pulse width). See Figure 2 for

example of transition. The figure was captured using a 4 quadrant supply (sinks and sources). See

optional battery cell replacement in Figure 3.

7. Verify that the IMON pin is between 930mV and 980 mV, DMM#3.

8. Verify that the VLDO output, DMM2, is between 4.4 V and 5.4 V.

9. Remove Shunt JP1 and verify that charging stops (input current reduces to near 3mA due to VLDO

load) and LED is flashing. This simulates a cold temperature fault.

10. Replace the JP1 shunt and verify the current returns to the default setting between 0.26 A and 0.31 A,

(270 - 310 mV on DMM#3).

11. Short between J2 TS and GND and verify a hot temperature fault with the LED flashing. Remove short

and verify that the current returns to the default setting between 0.26 A and 0.31 A.

12. Toggle S101 again to program the charge current to ~0.95A and let cell charge to completion. The

OUT should charge to 3.6 V then go into float mode where the regulation will be reduced to 3.5 VDC,

allowing the cell voltage to relax. This method of charging allows faster bulk charge.

NOTE: If the battery cell replacement circuit is used, the Cell voltage should be adjusted higher

slowly, via the Battery P/S, until the OUT voltage reaches ~3.6 V and the charge current

drops off. The OUT pin should relax some depending on the impedance of the diode in the

battery cell replacement circuitry. The Battery P/S voltage may have to be lowered slightly,

after output OV is reached, to get the OUT voltage to drop to the 3.5 V regulation

SLVU473– May 2011 1A, Single Cell LiFePO

Linear Battery Charger with 4.9 V, 50 mA LDO

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