The

µController is using A/D converters inputs PA6, PA7, PB2 and PB3 to measure respectively the voltages

on battery pack pins V/F1, C/F1, V/F2 and C/F2. Depending on these voltages the

µController will switch

various Open Drain pins to adjust the Voltage and Current regulation loops to the requirements of the

battery currently in charge.

Thus depending on the V/F pin voltage, the resistor R7 can be connected in parallel with R6 through PC4

which is configured in Open Drain mode. This will modify the resistor bridge R4, R6, and will set the voltage

regulation to 4.1V or 4.2V in respect with the battery type. The detection of the battery voltage is summarized

in Table 1. The 5% tolerance of the resistors, as well as the

±2 LSB accuracy of the Analog to Digital

Converter are taken into account for the calculation.

In a similar way, and depending on the C/F pin voltage, the charge current is set to match the requirements

of the battery. PC5, PC6 and PC7, configured in Open Drain mode, command the PNP transistors Q2

(PC5), Q3 (PC6) and Q4 (PC7). When Q2, Q3 or Q4 (or the three at the same time) are on, the current

control value is modified according to the resistor bridge (R11, R12) modification (R14, R15, R16 in parallel

with R11). The detection of the battery charge current is summarized in Table 2.

CURRENT FEEDBACK TO THE

µCONTROLLER :

One Operational Amplifier of the TSM102A is used to zoom the current that flows through the sense resistor

R0 (amplification loop R17, R19) so that this current information can be readable by the

µController. The

µController acquires the data though PB7 configured as and A/D input.

2 SLOTS CHARGING FLOW :

In this specific application the first slot (A) is made to receive a complete handy phone while the second

one (B) is made to accommodate a spare battery. Thus the user can charge both his phone + battery and

a replacement battery.

To ensure efficient charging of both batteries cells (which are connected in parallel), the

µController

commands two low Rdson P-channel MOSFETs alternatively (Q5 and Q6 with PB4 and PB5).

If only one of the slot receives a battery (either A or B) the charger will perform a standard charge of that

battery by switching on the corresponding MOSFET.

When the charger receives both the phone + battery (A) and the spare battery (B), the A slot has the priority.

Q5 will be turned on first and until A battery is full, B will be in Wait for Charge state, and Q6 will be off.

Only when A is full will B be charged (Q5 off, Q6 on). As the phone in slot A may be on, and thus its battery

may discharge as B is on charge, the voltage of A slot is continuously monitored. If a significant drop is

detected, then the charger will enter an alternate charging mode where both batteries are charged on a

time sharing basis, so as to always keep the phone battery in full condition.

USER INTERFACING :

The

µController drives directly 2 bicolor LEDs (one for each battery) through PA0, PA1, PA2, PA3. The

meaning of the different signals in given in Table 3.

Table 3 : USER INTERFACE LEDs

State

Green

Red

Bicolor Result

Remark

No battery

Off

Off

Off

each slot

Charging

Off

On

Red

each slot

Full

On

Off

Green

each slot

Wait for charge

On

On

Orange

B slot only

Battery fail

Blink

Blink

Orange Blink

each slot

Over/Under temperature

On

On

Orange

only when charging

AN1051 - APPLICATION NOTE

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