FUSB3317

www.onsemi.com

12

Figure 9. Protection Block Diagram

Buck or Buck−Boost

PWM Control

+

−

VBAT

CC2

VBUS

Protection Block

Enable Block

Discharge

DISC

DC_EN

EN

PWM

V1

OVP/UVP

E_OTP/I_OTP/OCP

CC_OVP/D_OVP

CC1

CC2

VDD

VDD

DC_EN

DC_EN pin is to disable/enable the external VBUS supply

IC like DC−DC converter. So, DC_EN connects to Enable

pin of DC−DC converter. To minimize the current

consumption of DC−DC converter while Sink is not plugged

in, FUSB3317 turns off the DC−DC until sink device

attaches. Once Sink attaches, FUSB3317 detects the CC

attach and enables DC_EN to High after 100msec of CC

debounce to supply VBUS. Also the CATH pin controls the

VBUS to 5 V default along with the DC_EN The initial

VBUS will be 5 Volt by default feedback and the voltage can

be changed following PD contract over CATH. DC_EN is

controlled to Low with sink detach or device reset by POR

or protection mode from OVP/OCP/OTP.

DON and USB2.0 Data Lines

The USB 2.0 Data Lines, D+ and D−, can be externally

connected together via a 100 ohms resistor to provide the

maximum power, a legacy USB device can take, which is

1.5 A per USB Battery Charging v1.2 (BC1.2) specification.

This will usually be the case when a USB−C to micro−B

cable is plugged into this design where this adapter cable has

the required Sink Rd resistors within it to allow the

FUSB3317 to recognize a Type C attach and to source 5 V

on VBUS. The Sink will go through BC1.2 steps of primary

and secondary detection to detect a Dedicated Charging Port

(DCP) via this resistor connection of D+ and D− and takes

1.5 A maximum from VBUS.

Internally, FUSB3317 presents BC1.2 Charging

Downstream Port(CDP) mode in default to provide the

1.5 A of power as well as to make USB signal path

connection between USB PHY, Head unit in automotive

application and sink device. Since USB data, D+, D−, path

have to connect from Sink to FUSB3317 as well as head unit,

there should be 2:1 switch mux externally. DON pin of

FUSB3317 can control the external switch enable or switch

direction control. Below diagram is the example of using

external switch, NIV1241, which has signal switch and TVS

diodes on D+ and D− for ESD protection.

Figure 10. DON Pin Connection to NIV1241

With sink attach, the FUSB3317 controls the DON pin

High to close the USB D+/D− signals between head unit and

the attached sink. DON pin is controlled to High about

900 ms after CC debounce and stayed high until sink device

is plugged out. DON pin controls to Low with sink detach

or device reset by POR or protection mode from

OVP/OCP/OTP.

BATUV

BATUV pin monitors VBAT, battery voltage, to know if

the voltage is low enough to send a new PD message to scale

down the negotiated source power data object. The pin can

be left float or either resistor divide input of VBAT. When

or when the BATUV is resistor divide of VBAT and then if

message will be sent to sink to renegotiate. In both cases, the

sending scale down message. The scaled down PDP(Power

Delivery Power) by VBAT UVP will be 75% of the max

PDP. For example, at 60 W PDP default, it will change to

45 W by VBAT UVP. Once VBAT UVP is recovered, it will

come back to 60 W.

NTC

NTC pin is to detect external temperature on the board.

NTC will connect to a thermistor which can be placed in the

hottest place on the PCB, it could be next to NFET or close

to the USB−C connector. Once NTC temperature rises to

warning range which is 90

°C, the scale down PDP will be

sent to sink so that the sink will pull less current/power. The

scale is the same as VBAT UVP, 75%. If the NTC detects

above shut down temperature, 100

°C, FUSB3317 enters

fault protection mode and VBUS FET will be shut off and

Sink will be disconnected.

The new PDP table is below in case of either VBAT UVP

or NTC. The PDP scaling minimum is 25% of PDP and PDP

scaling default is 75%.

VBAT−UVP NTC Warning

Resultant_PDP

Yes

No

PDP_scaling*Current_PDP

No

Yes

PDP_scaling*Current_PDP

Yes

Yes

PDP_scaling minimum

*Current_PDP

No

No

Current_PDP