www.ti.com
3.3V_OUT
VEXT
GATE
EN_REG
DP0_RST
Power Good (PG)
PG_DLY
BP_DIS
BPMODE or BPMODE
SLVS287B – SEPTEMBER 2000 – REVISED SEPTEMBER 2007
The internal 3.3-V LDO output can be used to supply up to 100 mA of current to low-power functions, such as
hub controllers.
VEXT is used to generate a 5-V source for the SP input by using the internal LDO controller and an external
N-channel MOSFET. This pin connects to a 6-V to 9-V power supply and to the drain of the MOSFET if the
external LDO is needed.
GATE is the output of the 5-V LDO controller and connects to the gate of the external MOSFET.
The active-high input, EN_REG, is used to enable the 5-V regulator controller. EN_REG is compatible with TTL
and CMOS logic levels.
DP0_RST functions as a hub reset when a 1.5-k
resistor is connected between DP0_RST and the upstream
DP0 data line in a hub system. To provide a clean attach signal on the 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 the high-impedance state and finally outputs a high signal. The low and Hi-Z pulse durations 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 transition high at the same time.
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 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, see the USB hub controller data sheet to determine the required
pulse-duration criteria.
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 switches to self-powered operation automatically; if the SP voltage falls lower than the
UVLO threshold, the device switches to bus-powered operation. When BP_DIS is connected high, the
autoswitching function is disabled and the device does not autoswitch to bus-powered operation if the SP voltage
is below the UVLO threshold.
BPMODE (TPS2070) or BPMODE (TPS2071) 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 TPS2070, BPMODE outputs a
low signal to indicate bus-powered mode or a high signal to indicate self-powered mode. For the TPS2071,
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.
Copyright 2000–2007, Texas Instruments Incorporated
5