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TPD4S014

www.ti.com

SLVSAU0B

– MAY 2011 – REVISED OCTOBER 2011

GENERAL OPERATION

The TPD4S014 provides a single-chip protection solution for USB charger interfaces. The VBUS line is tolerant

At power-up, when the voltage on VBUS is rising, the switch will close 16 ms after the input crosses the

undervoltage threshold, thereby making power available to the downstream circuits. The TPD4S014 also has an

ACK output, which deasserts to alert the system that a fault has occurred. The TPD4S014 offers 4 channel ESD

clamps for D+, D-, ID, and VBUS pins that provide IEC61000-4-2 level 4 ESD protection. This eliminates the

need for external TVS clamp circuits in the application.

The TPD4S014 has an internal oscillator and charge pump that controls the turn-on of the internal nFET switch.

The internal oscillator controls the timers that enable the turn-on of the charge pump and sets the state of the

charge pump. The charge-pump at startup, after a 16ms internal delay, turns on the internal nFET switch and

is disabled.

removing power to the application. The ACK signal is asserted when a fault condition is detected. If the fault was

remains above VUVLO. If the fault was an under voltage event, the switch turns on 16ms after the voltage

A 16ms deglitch time has been introduced in to the turn on sequence to ensure that the input supply has

stabilized before turning the switch ON. Noise on the Vbus line, could turn on the switch when the fault condition

is still active. To avoid this, OVP glitch immunity allows noise on the VBUS line to be rejected. Such a glitch

protection circuitry is also introduced in the turn off sequence in order to prevent the switch from turning off for

voltage transients. The glitch protection circuitry integrates the glitch over time, allowing the OVP circuitry to

trigger faster for larger voltage excursions above the OVP threshold and slower for shorter excursions. The

protection circuitry has a maximum delay of 8

µs.

When the device is ON, current flowing through the device will cause the device to heat up. Over heating can

lead to permanent damage to the device. To prevent this, an over temperature protection has been designed into

the device. Whenever the junction temperature exceeds 145

°C, the switch will turn off, thereby limiting the

temperature. The ACK signal will be asserted for an over temperature event. Once the device cools down to

below 120

°C the ACK signal will be deasserted, and the switch will turn on if the EN is active and the VBUS

voltage is within the UVLO and OVP thresholds. While the over temperature protection in the device will not

kick-in unless the die temperature reaches 145

°C, It is generally recommended that care is taken to keep the

junction temperature below 125

°C. Operation of the device above 125 °C for extended periods of time can affect

the long-term reliability of the part.

The junction temperature of the device can be calculated using below formula:

(1)

=

Junction temperature

=

Ambient temperature

=

Thermal resistance

=

Power Dissipated in device

(2)

I

=

Current through device

=

Max on resistance of device

Copyright

© 2011, Texas Instruments Incorporated

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