SM72445 Evaluation module Design Specification
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Figure 5. Load Connect and Stand-By Sequence After Start-Up
When a load is already present on the output of the board, the SM72445 will increase the duty cycle and
immediately enable MPPT operation when the voltages on AIOUT and AIIN rise above the internal
threshold.
INTERNAL CURRENT PROTECTION
If the voltage at AIOUT rises above the value set in A4, the system will reset. If AIOUT is set at or above
VDDA, this feature will be de-activated. The default setting for this board has this feature de-activated.
Current protection is performed using an external comparator
BOARD CURRENT PROTECTION
The board features a current protection circuit with U11A activating the PM pin of the SM72445 and
forcing the PM mode bypass switch to turn on (or the bridge to switch to 1:1 operation if the board is
reconfigured) when the output current reaches 13.5A. The output current will then be limited by the input
(solar panel) current. It is important to verify that the maximum solar panel current does not exceed the
rating of the components.
TEMPERATURE PROTECTION
U2 and U3 are strategically placed near the highest source of heat in the system (Q1 and Q4). When the
temperature reaches the tripping point (120 C), the ICs will activate the PM mode of the SM72445 by
forcing the PM pin low.
OVER-VOLTAGE PROTECTION
U11B forces the SM72445 to reset if the output voltage rises above 44V.
PANEL MODE SWITCH
Q5 and Q6 form a bi-directional switch controlled by the SM72445 and driven by U13 through T1. The
SM72445 supplies a 440kHz square waveform to turn on the switch.
GATE DRIVER
U7 is a quad 3A gate driver (two high and two low). It contains high-side operational amplifiers and buffers
used to sense the input current for MPPT purposes.
HEATSINKING
SM72445 evaluation board does not come with a heatsink. Therefore, in order to run the evaluation board
at elevated power ratings, an appropriate heatsink should be added on Q1, Q2, Q3 and Q4 as well as
diode D1. Care must be taken to prevent electrical contact between the drains of the MOSFETs in the
process of proper heatsinking. At elevated power operation please note the increase in temperature
across these semiconductor devices.
TEST SETUP
To perform an evaluation on the SM72445 evaluation board, it is suggested that the user connect the
input to a SAS (Solar Array Simulator) and the output to a load bank, preferably in Current mode (Voltage
mode sometimes causes regulation issues with some electronic load when used with the evaluation
board). The following sequence can be used to verify the operation of the board:
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AN-2241 SM72445 Evaluation Board
SNVA649 – May 2012
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