Document Number: 002-08404 Rev *A

Page 13 of 40

MB39C831

MPPT Operation

When setting the charge mode, the internal pulse frequency is determined by the values of the capacitors C5/C6 and C7/C8

(see Figure 3-1), which are connected to the CSH1 pin, and the CSH2 pin.

During the period of high level of the internal pulse setting by the capacitors C5/C6 connected to the CHS1 pin, the release

voltage is measured. The capacitors C5/C6 latch the measured voltage level, the release voltage.

During the period of low level of the internal pulse setting by the capacitors C7/C8 connected to the CSH2 pin, the charge

current is determined in order to make the VDD pin's voltage equal to the MPPT setting voltage, then the charging operation

starts up. The MPPT setting voltage is calculated by the following equation.

(refer to Table 7-3 MPPT control)

When using the recommended pars, the frequency is set to 0.35Hz with 5% duty.

If not using the recommended parts, please be aware of the following points.

1.

・In general, laminated capacitances have leak current. If the inside pulse cycle setting by the capacitors

2.

C7/C8 were set too long, the voltage level of the capacitors C5/C6 would drop. There is a possibility that

3.

the MPPT value cannot be set correctly.

4.

・If the period of high level of inside pulse is set too short, setting by the capacitors C5/C6, the MPPT value

5.

cannot be set correctly due to a lack of the measurement time of the release voltage.

Figure 7-4 MPPT Operation

LX waveform

Charging Operation

Measurement of release voltage

No DC/DC operation

VDD pin

voltage

VOUT pin

voltage

Release voltage

Frequency 0.35Hz Duty 5%,

when using recommended parts

Chareging resume

Full charge detection

The period of high level is set

by capacitors C5 and C6.

MPPT setting voltage

The period of high level is set

by capacitors C7 and C8.

time

Internal Pulse