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It’s on the more pricy side of TI eFuses but the wide current range and flexibility in voltage will allow us to save costs by requiring fewer ICs if we can keep the same system working into the next-generation vehicle.
Note that we will want the circuit breaker variant of this eFuse and not the current limiting variant.
Calculated Component Values for eFuse Protection Functions
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$ I_{LOAD} (A) = \frac{V_{VIMONIMON}(\mu V)}{R_{IMON} (\Omega) * G_{IMON}(\mu A/A)}$ |
The G_IMON is a proportionality constant given in the electrical characteristics to be 243 uA/A.
Rearranging this to solve for the value of R_IMON that we wish to use… (as shown on p. 24 of the datasheet)
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$ R_{IMON} (\Omega) = \frac{V_{IMON}(\mu V)}{I_{LOAD} (A) * G_{IMON}(\mu A/A)}$ |
Plugg
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$G_{IMON}$ |
On page 24 of the TPS25983 datasheet, the following formula is also shown in terms of
Retry # of Attempts
Retry Delay
Slew Rate
The integrated output slew rate helps control large inrush current that could damage input connectors and other electrical components. The formula for determining the slew rate of a particular load capacitance is…
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$ SR(V/ms) = \frac{I_{INRUSH}(mA)}{C_{OUT}(\mu F)}$ |
According to the datasheet, the formula for determining the capacitance of a particular slew rate is…
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$ C_{dVdt} (pF) = \frac{4600}{SR(V/ms)}$ |
It is recommended to select a capacitor with a value 20% higher than the calculated one and then choose the closest available capacitor from the 10% tolerance series. This is because the dV/dt capacitor experiences approximately VIN + 4 V during startup, and the high voltage bias causes a reduction in the effective capacitance.
Overvoltage Lockout
According to the datasheet, the formula for determining the OVLO for a given power supply is…
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$ V_{IN}(OV) = \frac{V_{OV}(R)*(R1+R2)}{R2}$ |
The eFuse turns OFF the power to the output when the voltage at the OVLO pin is greater than the OVLO rising threshold, VOV(R). The output power is turned ON again after the voltage at the OVLO pin falls below the OVLO falling threshold, VOV(F).
Overvoltage Protection (OVLO) | Min (V) | Typ (V) | Max (V) |
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VOV(R) | 1.1 | 1.21 | 1.25 |
VOV(F) | 1.08 | 1.1 | 1.125 |
Gate Resistance (for external FET)
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