P9221-R Datasheet

© 2017 Integrated Device Technology, Inc.

17

April 4, 2017

8.3

SINK Pin

The P9221-R has an internal automatic DC clamping to protect the device in the event of high voltage transients. The VRECT node must be

connected to the SINK pin at all times using a 36Ω resistor with a greater than ¼ W rating.

8.4

Rectifier Voltage – VRECT

The P9221-R uses a high‐efficiency synchronous rectifier to convert the AC signal from the coil to a DC signal on the VRECT pin. During startup,

the rectifier operates as a passive diode bridge. Once the voltage on VRECT exceeds the under-voltage lock-out level (UVLO; see Table 5),

the rectifier will switch into full synchronous bridge rectifier mode. A total capacitance of 30μF is recommended to minimize the output voltage

ripple.

8.5

Over-Current Limit – ILIM

The P9221-R has a programmable current limit function for protecting the device in the event of an over-current or short-circuit fault condition.

When the output current exceeds the programmed threshold, the P9221-R will limit the load current by reducing the output voltage. The current

limit should be set to 130% of the target maximum output current. See the ILIM pin description in Table 1 for further information.

8.6

Interrupt Function – INT

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The P9221-R provides an open-drain, active-LOW interrupt output pin. It is asserted LOW when EN is HIGH or any of the following fault

conditions have been triggered: the die temperature exceeds 140°C, the external thermistor measurement exceeds the threshold (see section

8.9), or an over-current (OC) or over-voltage (OV) condition is detected.

During normal operation, the INT pin is pulled HIGH. This pin can be connected to the interrupt pin of a microcontroller. The source of the trigger

8.7

Enable Pin – EN

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The P9221-R can be disabled by applying a logic HIGH to the EN pin. When the EN pin is pulled HIGH, the device is in Shut Down Mode.

Connecting the enable pin to logic LOW activates the device.

8.8

Thermal Protection

The P9221-R integrates thermal shutdown circuitry to prevent damage resulting from excessive thermal stress that may be encountered under

fault conditions. This circuitry will shut down or reset the P9221-R if the die temperature exceeds 140°C.

8.9

External Temperature Sensing – TS

The P9221-R has a temperature sensor input, TS, which can be used to monitor an external temperature by using a thermistor. The built-in

comparator’s reference voltage was chosen to be 0.6V in the P9221-R, and it is used for monitoring the voltage level on the TS pin as described

by Equation 1.

NTC

R+NTC

Equation 1

Where NTC is the thermistor’s resistance and R is the pull-up resistor connected to VDD18 pin. The over–temperature shutdown is trigged

when the TS pin voltage is lower than 0.6V; for more information, see Figure 24.