SM72442 Datasheet, PDF (8/14 Pages) National Semiconductor (TI) – Programmable Maximum Power Point Tracking Controller for Photovoltaic Solar Panels

PARAMETER DEFINITIONS
Output Voltage Slew Rate Limit Settling Time: Time con-
stant of the internal filter used to limit output voltage change.
For fast slew rate, every 1V increase, the output voltage will
be held for 30 ms whereas in a slow slew rate, the output
voltage will be held for 62 ms for every 1V increase. (See
Figure 6).
Starting PM Time: After initial power-up or reset, the output
soft-starts and then enters Panel Mode for this amount of
time.
MPPT Exit Threshold and MPPT Start Threshold: These
are the hysteretic thresholds for Iout_th.
Starting Boost Ratio – This is the end-point of the soft-start
voltage ramp. 1:1 ratio means it stops when Vout = Vin, 1:1.2
means it stops when Vout = 1.2 x Vin.
PANEL MODE PIN (PM) PIN
The SM72442 can be forced into Panel Mode by pulling the
PM pin low. One sample application is to connect this pin to
the output of an external temperature sensor; therefore when-
ever an over-temperature condition is detected the chip will
enter a Panel Mode.
Once Panel Mode is enabled either when buck-boost mode
is entered for a certain period of time (adjustable on channel
2 of ADC) or when PM is pulled low, the PM_OUT pin will
output a 400 kHz square wave signal. Using a gate driver and
transformer, this square wave signal can then be used to drive
a Panel Mode FET as shown in Figure 7.
FIGURE 6. Slew Rate Limitation Circuit
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FIGURE 7. Sample Application for Panel Mode Operation
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