Datasheet
www.ti.com
L = 0.9 mH, C
O
= 10 mF
− 500 mV/divV
O
V
I
= 3.6 V,
V
O
= 1.5 V,
I
O
= 0 mA
t − Time − 400 ms/div
EN − 2 V/div
L = 2.2 mH, C
O
= 4.7 mF,
− 1 V/divV
O
V
I
= 3.6 V,
V
O
= 1.6 V,
I
O
= 320 mA
V
t − Time − 50 ms/div
EN − 2 V/div
(ADJ)
− 2 V/div
I − 200 mA/div
L
DETAILED DESCRIPTION
OPERATION
TPS62300, TPS62301, TPS62302
TPS62303, TPS62304, TPS62305,
TPS62311, TPS62313, TPS62315, TPS62320, TPS62321
SLVS528E – JULY 2004 – REVISED NOVEMBER 2007
START-UP POWER DOWN (TPS62321)
Figure 29. Figure 30.
The TPS6230x, TPS6231x, and TPS6232x are synchronous step-down converters typically operating with a
3-MHz fixed frequency pulse width modulation (PWM) at moderate to heavy load currents. At light load currents,
the converter operates in power-save mode with pulse frequency modulation (PFM). The operating frequency is
set to 3 MHz and can be synchronized on-the-fly to an external oscillator.
During PWM operation, the converter uses a unique fast response, voltage mode, controller scheme with input
voltage feed-forward. This achieves best-in-class load and line response and allows the use of tiny inductors and
small ceramic input and output capacitors. At the beginning of each switching cycle, the P-channel MOSFET
switch is turned on and the inductor current ramps up until the comparator trips and the control logic turns off the
switch.
The device integrates two current limits, one in the P-channel MOSFET and another one in the N-channel
MOSFET. When the current in the P-channel MOSFET reaches its current limit, the P-channel MOSFET is
turned off and the N-channel MOSFET is turned on. When the current in the N-channel MOSFET is above the
N-MOS current limit threshold, the N-channel MOSFET remains on until the current drops below its current limit.
The current limit in the N-channel MOSFET is important for small duty-cycle operation when the current in the
inductor does not decrease because of the P-channel MOSFET current limit delay, or because of start-up
conditions where the output voltage is low.
Copyright © 2004 – 2007, Texas Instruments Incorporated Submit Documentation Feedback 15
Product Folder Link(s): TPS62300, TPS62301, TPS62302 TPS62303, TPS62304, TPS62305, TPS62311, TPS62313,
TPS62315, TPS62320, TPS62321