Datasheet

T
J
− Junction Temperature − °C
0
1
2
3
4
5
6
−50 0 50 100 150
I
q
− Bias Current − µA
G007
V
IN
= 3.3 V
V
IN
− Input Voltage − V
0
1
2
3
4
5
6
7
8
9
0 1 2 3 4 5 6
I
q
− Bias Current − µA
G008
T
J
= −40°C
T
J
= 85°C
T
J
= 25°C
TPS2500, TPS2501
www.ti.com SLVS886C –OCTOBER 2008–REVISED AUGUST 2010
TYPICAL CHARACTERISTICS (continued)
Figure 9. Bias Current vs Junction Temperature, Figure 10. Bias Current vs Input Voltage,
V
IN
= 3.3 V, V
EN
= 0 V (Disabled) V
EN
= 0 V (Disabled)
THEORY OF OPERATION
DESCRIPTION
This device targets applications for host-side USB devices where a 5-V power rail, required for USB operation, is
unavailable. The TPS2500 integrates the functionality of a synchronous boost converter and a single USB switch
into a monolithic integrated circuit so that lower-voltage rails can be used directly to provide USB power. An
additional feature is that the auxiliary 5-V power rail is brought external to the device to power non-USB loads in
addition to the integrated USB switch.
The boost converter is highly integrated, including the switching MOSFETs (low-side N-channel, high-side
synchronous P-channel), gate-drive and analog-control circuitry, and control-loop compensation. Additional
features include high-efficiency light-load operation, overload and short-circuit protection, and controlled
monotonic soft start. The USB switch integrates all necessary functions, including back-to-back series N-channel
MOSFETs, charge-pump gate driver, and analog control circuitry. The current-limit protection is user-adjustable
by selecting the R
ILIM
resistor from ILIM to GND.
The only external components required are the boost inductor, current-limit setting resistor, and input and output
capacitors for the boost converter.
BOOST CONVERTER
Start-Up
Input power to the TPS2500 is provided from IN to GND. The device has an undervoltage lockout (UVLO) circuit
that disables the device until the voltage on IN exceeds 2.15 V (typical). The TPS2500 goes through its normal
start-up process and attempts to regulate the AUX voltage to 5.1 V (typical).
The boost converter has a two-step start-up sequence. Step one is a constant-current mode that regulates the
current through the high-side P-channel MOSFET to I
START
(2.65 A typical). I
START
provides power to the load and
charges the output capacitance on V
AUX
until V
AUX
reaches V
IN
– V
EXIT
. The converter begins to switch once V
AUX
exceeds V
IN
– V
EXIT
. The initial duty cycle of the device is limited by a closed-loop soft start that ramps the
reference voltage to the internal error amplifier to provide a controlled, monotonic start-up on V
AUX
. The boost
converter goes through this cycle any time the voltage on V
AUX
drops below V
IN
– V
EXIT
due to overload
conditions or the boost converter re-enables after normal shutdown.
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Product Folder Link(s): TPS2500 TPS2501