Protection functions of TPS63070

Hi,

• Thermal shutdown:

The junction temperature (Tj) of the device is monitored by an internal temperature sensor. When Tj exceeds the thermal shutdown temperature, the device goes into thermal shutdown. The power stage is turned off and PG goes low. When Tj decreases below the hysteresis amount, the converter resumes normal operation, beginning with a Soft Start cycle. To avoid unstable conditions, a hysteresis of typically 20°C is implemented on the thermal shutdown temperature. In addition, the thermal shutdown is debounced by approximately 10 μs.

• Overvoltage protection:

TPS6307x has a built in over-voltage protection which limits the output voltage. The voltage is internally sensed on the VOUT pin. In case the voltage on the feedback pin is not set correctly or the connection is open, this limits the output voltage to a value that protects the output stage from a too high voltage by limiting it to a internally set value. Input over-voltage protection forces PFM mode to make sure the device is protected against boosting from the output to the input. This may happen if there is a large capacitor charged above the nominal voltage on the output and the supply on the input is removed. In PWM mode, the device is able to provide current from the output to the input causing a rise in the input voltage. In PFM mode, the current to the input is blocked so the input voltage can not rise. The input over-voltage protection does not protect the device from a too high voltage applied to the input but just from operating such that the device itself causes a rise of the input voltage above critical levels. Both over-voltage sensors are de-glitched by approximately 1μs.

• Undervoltage lockout:

When the input voltage drops, the undervoltage lockout prevents mis-operation by switching off the device. The converter starts operation when the input voltage exceeds the threshold by a hysteresis of typically 850 mV. This relatively large hysteresis is needed to allow operation down to 2-V of supply voltage for the case when the output voltage is up at 3-V or above but restrict start-up for the case when the output voltage is zero. For start-up when the output voltage has not yet ramped, the rising UVLO threshold was set to a level that allows to start TPS63070 at a supply voltage where the load does not demand much load current.

• Short circuit protection:

The TPS6307x provides short circuit protection to protect itself and the application. When the output voltage is below 1.2 V, the back-gate diodes of the low side input FET and high side output FET are used for rectification. For an input voltage above 9 V and an output voltage below 2.2 V, the switching frequency is scaled to ½ of its nominal value.

Would you please explain this: My customer tried to input enable pin again when oerate of IC is not normal.?

What are the test conditions?

What does it mean operate of IC is not normal?

Would you please provide oscilloscope screenshoot:

• voltage pin L1
• voltage pin L2
• inductor current L
• EN pin signal

Best regards

Lubomir

Thank you for your answer.

My customer tests TPS63070 under the following conditions.

Vin=7~16V
Vout=6.5V
Iout=2A(max)


But the IC stops operation.

Customer changes Enable pin from High to Low.
But 6 V continues to be output.(in this condition, output current is 0A.)

Customer changes Enable pin from Low to High.
But 6V is still output.(in this condition, output current is 0A.)

When the customer applies the current(200~300mA),the output voltage keeps decreasing.

When Customer did hard reset , the IC recovers.

My customer wants to know if a hard reset is included in the return condition from protected state to normal operation.
(the most important question)

My customer wants to know the conditions that protection function operates(Thermal shutdown,overvoltage protection,
UVLO,shortcircuit protection).
And My customer wants to know how the IC recovers from protected state to normal operation.

Please tell me the anwer of these questions.

Best Regards

Hi Takahiro,

1. Customer changes Enable pin from High to Low.
   But 6 V continues to be output.(in this condition, output current is 0A.) In this conditions output capacitor is charger to 6.5V and will be discharged by the current flowing through voltage divider and leakage current of the output capacitor and load.
2. Customer changes Enable pin from Low to High.
   But 6V is still output.(in this condition, output current is 0A.) This is strange not expected behavior because device is enabled and should start to switch and regulate output voltage according to the figure 48 in the datasheet.
3. There is no requirement for example for overload current on the output to recover from protected state to normal switching mode.

Questions:

1. Would you please provide schematic and layout of the customer application?
2. Can customer test the same conditions on the EVM?
3. Why does customer use buck boost converter for step down conversion of the input voltage?
   
   1. is input voltage still higher than the output voltage?
4. Will be possible to get waveforms which I asked in the previous message?

Best regards

Lubomir

Thank you for your answer

1. Would you please provide schematic and layout of the customer application?

   ⇒Aplication is Camera.

   　Please check the documentation.

2. Can customer test the same conditions on the EVM?

   ⇒My customer uses this IC on customer's board.

3. Why does customer use buck boost converter for step down conversion of the input voltage? 

             ⇒My customer tried to use other IC.But the duty of other IC is not enough.

　　　　I handed out TPS63070EVM in a separate case.

                My customer thought that TPS63070  can also be used in customer specifications.

                So customer tries to use TPS63070 at buck mode only.

         4.Will be possible to get waveforms which I asked in the previous message?

　　　⇒Please check the documentation.TPS63070 data.pdf