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Overvoltage Protection (OVP)

Undervoltage Lockout

Thermal Shutdown

TPS61042

SLVS441C – DECEMBER 2002 – REVISED MARCH 2007

DETAILED DESCRIPTION (continued)

As with any current source, the output voltage rises as the output impedance increases or is disconnected. To

prevent the output voltage from exceeding the maximum main switch (Q1) voltage rating of 30 V, an overvoltage

protection circuit is integrated. When the output voltage exceeds the OVP threshold voltage, (Q1) turns off. The

converter switch remains off until the output voltage falls below the OVP threshold voltage. As long as the output

voltage is below the OVP threshold the converter continues its normal operation, until the output voltage

exceeds the OVP threshold again.

An undervoltage lockout feature prevents mis-operation of the device at input voltages below 1.5 V (typ). As long

as the input voltage is below the undervoltage threshold the device remains off, with the main MOSFET switch

(Q1) and the LED switch (Q2) open.

An internal thermal shutdown is implemented in the TPS61042 that shuts down the device if the typical junction

temperature of 160

°C is exceeded. If the device is in thermal shutdown mode, the main MOSFET switch (Q1)

and the LED switch (Q2) are open.

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