Datasheet

2
V
OUT
ton = × 360ns × 2
V
IN
2 × I
OUT
=
V - V V - V
IN IN
OUT OUT
ton 1 + x
V L
OUT
f
æ ö
ç ÷
ç ÷
è ø
TLV62090
SLVSBB9B –MARCH 2012–REVISED APRIL 2012 www.ti.com
DETAILED DESCRIPTION
Operation
The TLV62090 synchronous switched mode converter is based on DCS™ Control (Direct Control with Seamless
transition into Power Save Mode). This is an advanced regulation topology that combines the advantages of
hysteretic and voltage mode control.
The DCS™ Control topology operates in PWM (Pulse Width Modulation) mode for medium to heavy load
conditions and in Power Save Mode at light load currents. In PWM, the converter operates with its nominal
switching frequency of 1.4 MHz having a controlled frequency variation over the input voltage range. As the load
current decreases, the converter enters Power Save Mode, reducing the switching frequency and minimizing the
IC quiescent current to achieve high efficiency over the entire load current range. DCS™ Control supports both
operation modes (PWM and PFM) using a single building block having a seamless transition from PWM to Power
Save Mode without effects on the output voltage. The TLV62090 offers excellent DC voltage regulation and load
transient regulation, combined with low output voltage ripple, minimizing interference with RF circuits.
PWM Operation
At medium to heavy load currents, the device operates with pulse width modulation (PWM) at a nominal
switching frequency of 1.4 MHz. As the load current decreases, the converter enters the Power Save Mode
operation reducing its switching frequency. The device enters Power Save Mode at the boundary to
discontinuous conduction mode (DCM).
Power Save Mode Operation
As the load current decreases, the converter enters Power Save Mode operation. During Power Save Mode the
converter operates with reduced switching frequency in PFM mode and with a minimum quiescent current while
maintaining high efficiency. The Power Save Mode is based on a fixed on-time architecture following Equation 1.
(1)
In Power Save Mode the output voltage rises slightly above the nominal output voltage in PWM mode, as shown
in Figure 5. This effect can be reduced by increasing the output capacitance or the inductor value. This effect can
also be reduced by programming the output voltage of the TLV62090 lower than the target value. As an
example, if the target output voltage is 3.3 V, then the TLV62090 can be programmed to 3.3V - 0.8%. As a result
the output voltage accuracy is now -2.2% to +2.2% instead of -1.4% to 3%. The output voltage accuracy in PFM
operation is reflected in the electrical specification table and given for a 22 µF output capacitance.
Low Dropout Operation (100% Duty Cycle)
The device offers low input to output voltage difference by entering 100% duty cycle mode. In this mode the high
side MOSFET switch is constantly turned on. This is particularly useful in battery powered applications to achieve
longest operation time by taking full advantage of the whole battery voltage range. The minimum input voltage
where the output voltage falls below its nominal regulation value is given by:
V
IN(min)
= V
OUT(max)
+ I
OUT
x ( R
DS(on)
+ R
L
) (2)
10 Submit Documentation Feedback Copyright © 2012, Texas Instruments Incorporated
Product Folder Link(s): TLV62090