Datasheet
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Outputvoltage
Vout (PWM)
Vout +1%
PFMComparator
threshold
VoltagePositioning
Lightload
PFMMode
moderatetoheavyload
PWMMode
100% Duty Cycle Low Dropout Operation
Undervoltage Lockout
MODE SELECTION
TPS62290 , TPS62291 , TPS62293
SLVS764C – JUNE 2007 – REVISED MARCH 2008
Figure 19. Power Save Mode Operation
The device starts to enter 100% duty cycle Mode once the input voltage comes close the nominal output voltage.
To maintain the output voltage, the High Side MOSFET switch is turned on 100% for one or more cycles.
With further decreasing VIN the High Side MOSFET switch is turned on completely. In this case, the converter
offers a low input-to-output voltage difference. 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 to maintain regulation depends on the load current and output voltage, and can be
calculated as:
V
IN
min = V
O
max + I
O
max × R
DS(on)
max + R
L
)
With:
I
O
max = maximum output current plus inductor ripple current
R
DS(on)
max = maximum P-channel switch R
DS(on)
.
R
L
= DC resistance of the inductor
V
O
max = nominal output voltage plus maximum output voltage tolerance
The undervoltage lockout circuit prevents the device from malfunctioning at low input voltages and from
excessive discharge of the battery and disables the output stage of the converter. The undervoltage lockout
threshold is typically 1.85V with falling V
IN
.
The MODE pin allows mode selection between forced PWM mode and Power Save Mode.
Connecting this pin to GND enables the Power Save Mode with automatic transition between PWM and PFM
mode. Pulling the MODE pin high forces the converter to operate in fixed frequency PWM mode even at light
load currents. This allows simple filtering of the switching frequency for noise sensitive applications. In this mode,
the efficiency is lower compared to the power save mode during light loads.
The condition of the MODE pin can be changed during operation and allows efficient power management by
adjusting the operation mode of the converter to the specific system requirements.
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