RB1

RT1 + RB1

x

(RFB1 + RFB2)

RFB2

SM72441

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SNOSB64G – OCTOBER 2010 – REVISED APRIL 2013

Figure 5. Start-Up Waveforms of Controlled Output

MAXIMUM OUTPUT VOLTAGE

Maximum output voltage on the SM72441 is set by resistor divider ratio on pin A0. (Please refer to Figure 2

Typical Application Circuit).

(1)

Where RT1 and RB1 are the resistor divider on the ADC pin A0 and RFB1 and RFB2 are the output voltage

feedback resistors. A typical value for RFB2 is about 2 k

Ω.

CURRENT LIMIT SETTING

Maximum output current can be set by changing the resistor divider on A4 (pin 18). (Refer to Figure 2 ).

Overcurrent at the output is detected when the voltage on AIOUT (pin 21) equals to the voltage on A4 (pin 18).

The voltage on A4 can be set by a resistor divider connected to 5V whereas a current sense amplifier output can

be used to set the voltage on AIOUT.

AIIN AND AIOUT PIN

These two pins are used to set current threshold from standby (buck-boost mode) to MPPT mode and from

MPPT mode into standby mode.

In order to transition from standby to MPPT mode, the following conditions have to be satisfied:

1) AIIN and AIOUT voltage > 0.488V

2) Iout < Iout_max

On the other hand, in order to transition from MPPT to standby mode, the following condition have to be

satisfied:

1) AIIN and AIOUT voltage < 0.293V

2) Iout < Iout_max

Current limit is triggered when AIOUT (pin 21) voltage is equal to A4 (pin 18).

AVIN PIN

AVIN pin is an A/D input to sense the input voltage of SM72441. A resistor divider can be used to scale the max

voltage to about 4V, which is 80% of the full scale of the A/D input.

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