FOUR-PORT USB HUB POWER CONTROLLERS
SLVS288A – SEPTEMBER 2000 – REVISED FEBRUARY 2001
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
INPUT VOLTAGE (SP UNDERVOLTAGE LOCKOUT)
TJ – Junction Temperature – °C
external capacitor requirements
µF ceramic bypass capacitor and a 10-µF bulk capacitor between BP and AGND, close to the device, are
recommended. Similarly, a 0.1-
µF ceramic and a 68-µF bulk capacitor, from SP to AGND, and from VEXT to
AGND if an external 5-V LDO is required, are recommended because of much higher current in the self-powered
From each of the outputs (OUTx) to ground, a 33-
µF or higher valued bulk capacitor is recommended when the
output load is heavy. This precaution reduces power-supply transients. Additionally, bypassing the outputs with
µF ceramic capacitor improves the immunity of the device to short-circuit transients.
An output capacitor connected between 3.3V_OUT and GND is required to stabilize the internal control loop.
The internal LDO is designed for a capacitor range of 4.7
µF to 33 µF with an ESR of 0.2 Ω to 10 Ω. Solid
tantalum-electrolytic, aluminum-electrolytic, and multilayer ceramic capacitors are all suitable.
Ceramic capacitors have different types of dielectric material, each exhibiting different temperature and voltage
variations. The most common types are X5R, X7R, Y5U, Z5U, and NPO. The NPO type ceramic capacitors are
generally the most stable over temperature. However, the X5R and X7R are also relatively stable over
temperature (with the X7R being the more stable of the two) and are therefore acceptable for use. The Y5U and
Z5U types provide high capacitance in a small geometry, but exhibit large variations over temperature. For this
reason, the Y5U and Z5U are not generally recommended.