SM72445

PM_OUT

PM

Pulse High

SM72482

IN_A

IN_B

2.00k

Square Wave

VCC

VEE

10V

0.47 PF

OUT_A

OUT_B

10k

499 0.47 PF

150 pF

499

10k

PV (+)

VOUT (+)

Panel Mode FETs

20 - 40ms

(Frequency

dependent)

Fast

Slow

No Slew

600 ms

1200 ms

40V

30V

'V = 10V

SM72445

SNVS795 – MARCH 2012

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MPPT Exit Threshold and MPPT Start Threshold: These are the hysteretic thresholds for Iout_th read on pin

AIOUT. The values are expressed as a fraction of the voltage at pin VDDA. AIOUT is the output current sensing

pin and should be connected to the output of a current sense amplifier. For example, with a current sense

amplification of 0.5V/A provided by an external current sense resistor and amplifier and assuming VDDA=5V and

A6=0.94V, the output current threshold to bring the device out of stand-by mode will be 0.39A.

Starting Boost Ratio: This is the end-point of the soft-start voltage ramp expressed as a ratio of VOUT/VIN. 1:1

ratio means it stops when Vout = Vin, whereas a 1:1.2 ratio means it stops when Vout = 1.2 x Vin.

DEAD-TIME

The dead time of the switches to avoid cross conduction of the buck FETs and boost FETs depends on the

dead time between HIA and LOA and between HIB and LOB will be 55ns.

PANEL MODE PIN (PM)

The SM72445 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 whenever an over-temperature condition is

detected the chip will enter Panel Mode.

Once Panel Mode is enabled, either when the unit is running in MPPT mode with a 1:1 conversion ratio or when

PM is pulled low, the PM_OUT pin will output a 440 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 11.

Figure 10. Slew Rate Limitation Circuit

Figure 11. Sample Application for Panel Mode Operation

RESET PIN

When the reset pin is pulled low, the chip will cease its normal operation and turn-off all of its PWM outputs

including the output of PM_OUT pin. Below is an oscilloscope capture of a forced reset condition.

10

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