P9221-R Datasheet

© 2017 Integrated Device Technology, Inc.

17

October 10, 2017

Table 6.

Setting the Output Voltage and Reference Q-factor Value

Q Factor

Value Setting

VOUT Setting(R34/R33 Values)

9V without 5V

9V with 5V

12V without 5V

12V with 5V

R34

R33

R34

R33

R34

R33

R34

R33

103

10kΩ

4.87kΩ

Open

10kΩ

10kΩ

21kΩ

10kΩ

Open

80

10kΩ

4.32kΩ

10kΩ

0.31kΩ

10kΩ

22.6kΩ

10kΩ

324kΩ

60

10kΩ

3.65kΩ

10kΩ

0.681kΩ

10kΩ

27.4kΩ

10kΩ

147kΩ

40

10kΩ

3.09kΩ

10kΩ

1.1kΩ

10kΩ

32.4kΩ

10kΩ

90.9kΩ

20

10kΩ

2.55kΩ

10kΩ

1.54kΩ

10kΩ

39.2kΩ

10kΩ

64.9kΩ

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. A 0.1uF capacitor is added for decoupling.

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 (see Figure 11), the P9221-R will limit the load current by reducing the output

voltage. The current limit should be set to 120% of the target maximum output current. See the ILIM pin description in Table 1 for further

information. The ILIM pin allows changing the over-current limit value without modification of the firmware by selecting the values of R38 and

R22 as shown in Table 7.

Table 7. Setting the Over Current Limit

Voltage on ILIM Pin [V]

R38 [kΩ]

R22 [kΩ]

Output Current [A]

Over-Current Limit [A]

Pull-up

10

Open

1.25

1.6

0.60

10

5.1

0.80

1

0.45

10

3.3

0.64

0.8

0.25

10

1.6

0.40

0.5