Datasheet

SM72442

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SNVS689H –OCTOBER 2010–REVISED APRIL 2013

Different conditions to enter and exit Panel Mode can be set on the ADC input channel 2. Listed below are

different conditions that a user can select on pin A2. “1:1” refers to the state in which the DC/DC converter

operates with its output voltage equal to its input voltage (also referred to as “Buck-Boost” mode in Figure 4.)

A2 Entering Panel Mode Exiting Panel Mode

4.69 V 2s in 1:1 Mode 3.1% power variation

4.06 V 1s in 1:1 Mode 3.1% power variation

3.44 V 0.4s in 1:1 Mode 3.1% power variation

2.81 V 0.2s in 1:1 Mode 3.1% power variation

2.19 V 2s in 1:1 Mode 1.6% power variation

1.56 V 1s in 1:1 Mode 1.6% power variation

0.94 V 0.4s in 1:1 Mode 1.6% power variation

0.31 V 0.2s in 1:1 Mode 1.6% power variation

The user can also select the output voltage slew rate, minimum current threshold and duration of Panel Mode

after the soft-start period has finished, by changing the voltage level on pin A6 which is the input of ADC channel

A6 Output Voltage Starting Panel Mode MPPT Exit MPPT Start Starting boost ratio

Slew Rate Limit Time Threshold Threshold

4.69 V Slow Not applicable 0 mA 0 mA 1:1

4.06 V Slow 60s 75mA 125mA 1:1

3.44 V Slow 0s 300mA 500mA 1:1

2.81 V Slow 120s 300mA 500mA 1:1

2.19 V Slow Not applicable 300mA 500mA 1:1.2

1.56 V Slow 60s 300mA 500mA 1:1

0.94 V Fast 60s 300mA 500mA 1:1

0.31 V No slew rate limit 60s 300mA 500mA 1:1

PARAMETER DEFINITIONS

Output Voltage Slew Rate Limit Settling Time: Time constant 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 whenever 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.

Product Folder Links: SM72442