TPS2074, TPS2075

FOUR-PORT USB HUB POWER CONTROLLERS

SLVS288A – SEPTEMBER 2000 – REVISED FEBRUARY 2001

4

POST OFFICE BOX 655303

detailed description

BP

The bus-powered supply input (BP) serves as the source for the internal 3.3-V LDO and for all logic functions

in the device. In bus-powered mode, BP also serves as the source for all the outputs (OUTx). If BP is below the

undervoltage threshold, all power switches will turn off and the LDO will be disabled. BP must be connected to

a voltage source in order for the device to operate.

SP

The self-powered supply input (SP) serves as the source for all the outputs (OUTx) in self-powered mode. The

enable logic for the SP switches requires that BP be connected to a voltage source.

OUT1, OUT2, OUT2, OUT4

OUTx are the outputs of the integrated power switches.

3.3V_OUT

The internal 3.3-V LDO output can be used to supply up to 100 mA current to low-power functions, such as hub

controllers.

DP0_RST

DP0_RST functions as a hub reset when a 1.5-k

Ω resistor is connected between DP0_RST and the upstream

DP0 data line in a hub system. To provide a clean attach signal on DP0 data line, the DP0_RST output goes

low momentarily (because of the upstream pulldown resistor) to discharge any parasitic charge on the cable,

then goes to 3-state and finally outputs a high signal. The low and Hi-Z pulse widths are adjustable using a

capacitor between PG_DLY and ground, and are approximately 50% of the power-good time delay. Detachment

is signaled by a Hi-Z on DP0_RST. Both DP0_RST and PG will transition high at the same time.

Power Good (PG)

The power good (PG) function serves as a reset for a USB hub controller. PG is asserted low when the output

voltage on the internal voltage regulator is below a fixed threshold. A time delay to ensure a stable output voltage

before PG goes high is adjustable using a small-value ceramic capacitor from PG_DLY to ground.

PG_DLY

PG_DLY connects to an external capacitor to adjust the time delay for PG and DP0_RST. For USB applications,

a 0.1

µF capacitor is recommended, however, reference the USB hub controller data sheet to determine the

needed pulse width criteria.

BP_DIS

BP_DIS is used to enable or disable the autoswitching function between bus-powered mode and self-powered

mode. When BP_DIS is connected low and the voltage on SP is greater than the undervoltage-lockout (UVLO)

threshold, the device will switch to self-powered operation automatically; if the SP voltage falls lower than the

UVLO threshold, the device will switch to bus-powered operation. When BP_DIS is connected high, the

autoswitching function is disabled and the device will not autoswitch to bus-powered operation if the SP voltage

is below the UVLO threshold.

BPMODE or BPMODE

BPMODE (TPS2074) or BPMODE (TPS2075) is an output that signals when the device is in bus-powered

mode. The logic state is set according to the voltages on BP, SP, and BP_DIS. For the TPS2074, BPMODE

outputs a low signal to indicate bus-powered mode or a high signal to indicate self-powered mode. For the

TPS2075, BPMODE outputs a high signal to indicate bus-powered mode or a low signal to indicate self-powered

mode. This output can be used to inform a USB hub controller to configure for bus-powered mode or

self-powered mode.