DC Current (A)
P
P_E
XT
P
ow
er
Los
s
(mW
)
3
3.2
3.4
3.6
3.8
4
4.2
4.4
4.6
4.8
5
0
100
200
300
400
500
600
700
800
900
1000
D012
77
SLVSDC2B – FEBRUARY 2016 – REVISED AUGUST 2016
Product Folder Links:
Copyright © 2016, Texas Instruments Incorporated
10.2.1.3 Application Curve
Figure 75. PP_EXT Power Loss (R
NFETS
+ R
SENSE
= 30 m
Ω
)
10.2.2 USB Type-C and PD Dock or Monitor Application
The TPS65981 controls two separate power paths making it a flexible option for Type-C and PD dock application
that simultaneously charges a USB PD DisplayPort video source (for example, a notebook computer). The dock
or monitor application of the TPS65981, shown in
, uses a GPIO to sense when a power supply is
present on the system-side of the TPS65981. When external power is applied from an AC-DC power supply first,
the TPS65981 shall be configured to automatically attempt to become the USB Type-C or PD power source.
When a notebook computer or other USB PD source is connected first and the AC-DC supply is not present, the
dock or monitor supports booting from VBUS in No Battery Mode, provides power to the SPI Flash to load
application code, and can optionally power the entire system by enabling the PP_EXT path as a sink. If the AC-
DC power supply is applied at a later time, the TPS65981 will detect the new power supply, automatically enable
one of more Source PDOs, and initiate a Power Role Swap PD message to offer power to the system at the far-
end of the Type-C cable. Refer to
for a timing diagram of the GPIO-controlled variable buck regulator
voltage output at PP_HV and the voltage at VBUS during a Type-C connection and throughout an intial USB PD
power negotiation where the dock or monitor is the power source. The video receptacle can be DisplayPort,
HDMI, or VGA although only DisplayPort is shown in
. The dock or monitor application uses a Type-C
receptacle and an HD3SS460 SuperSpeed multiplexer that is controlled by the TPS65981. The CC1/2 pins of the
TPS65981 will detect cable orientation and automatically configure the HD3SS460 SuperSpeed signal pairs for
2-lanes of USB3 data and 2-lanes of DisplayPort video or 4-lanes of DisplayPort video depending on the
Alternate Mode configured by the downstream-facing port (DFP).
