Datasheet

ON
OUTIN
peakLPSM
t
L
VV
I ×
-
=
)(
)(
TPS62160
TPS62161, TPS62162, TPS62163
SLVSAM2C NOVEMBER 2011REVISED SEPTEMBER 2013
www.ti.com
DETAILED DESCRIPTION
Device Operation
The TPS6216X synchronous switched mode power converters are based on DCS-Control™ (Direct Control with
Seamless Transition into Power Save Mode), an advanced regulation topology, that combines the advantages of
hysteretic, voltage mode and current mode control including an AC loop directly associated to the output voltage.
This control loop takes information about output voltage changes and feeds it directly to a fast comparator stage.
It sets the switching frequency, which is constant for steady state operating conditions, and provides immediate
response to dynamic load changes. To get accurate DC load regulation, a voltage feedback loop is used. The
internally compensated regulation network achieves fast and stable operation with small external components
and low ESR capacitors.
The DCS-Control
TM
topology supports PWM (Pulse Width Modulation) mode for medium and heavy load
conditions and a Power Save Mode at light loads. During PWM, it operates at its nominal switching frequency in
continuous conduction mode. This frequency is typically about 2.25MHz with a controlled frequency variation
depending on the input voltage. If the load current decreases, the converter enters Power Save Mode to sustain
high efficiency down to very light loads. In Power Save Mode the switching frequency decreases linearly with the
load current. Since DCS-Control
TM
supports both operation modes within one single building block, the transition
from PWM to Power Save Mode is seamless without effects on the output voltage.
Fixed output voltage versions provide smallest solution size and lowest current consumption, requiring only 3
external components. An internal current limit supports nominal output currents of up to 1A.
The TPS6216X family offers both excellent DC voltage and superior load transient regulation, combined with
very low output voltage ripple, minimizing interference with RF circuits.
Pulse Width Modulation (PWM) Operation
The TPS6216X operates with pulse width modulation in continuous conduction mode (CCM) with a nominal
switching frequency of about 2.25MHz. The frequency variation in PWM is controlled and depends on V
IN
, V
OUT
and the inductance. The device operates in PWM mode as long the output current is higher than half the
inductor's ripple current. To maintain high efficiency at light loads, the device enters Power Save Mode at the
boundary to discontinuous conduction mode (DCM). This happens if the output current becomes smaller than
half the inductor's ripple current.
Power Save Operation
The TPS6216X's built in Power Save Mode will be entered seamlessly, if the load current decreases. This
secures a high efficiency in light load operation. The device remains in Power Save Mode as long as the inductor
current is discontinuous.
In Power Save Mode the switching frequency decreases linearly with the load current maintaining high efficiency.
The transition into and out of Power Save Mode happens within the entire regulation scheme and is seamless in
both directions.
The TPS6216X includes a fixed on-time circuitry. This on-time, in steady-state operation, can be estimated as:
(1)
For very small output voltages, the on-time increases beyond the result of Equation 1, to stay above an absolute
minimum on-time, t
ON(min)
, which is around 80ns to limit switching losses. The peak inductor current in PSM can
be approximated by:
(2)
When V
IN
decreases to typically 15% above V
OUT
, the TPS6216X will not enter Power Save Mode, regardless of
the load current. The device maintains output regulation in PWM mode.
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Product Folder Links: TPS62160 TPS62161 TPS62162 TPS62163