]

Hz

[

f

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100

ns

70

DC

SW

min

×

×

=

(

)

IN

2

PEAK

OUT

IN

OUT

OUT

)

PSM

(

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V

I

L

V

V

V

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×

×

-

×

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=

10

TPSM82480

SLVSDT1 – JULY 2017

www.ti.com

Product Folder Links: TPSM82480

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Copyright © 2017, Texas Instruments Incorporated

Feature Description (continued)

7.3.8 Active Output Discharge

The VO pin, connected to the output voltage, provides an active discharge path when the device is switched off

by setting EN Low or UVLO event. In case of being activated, this discharge circuit sinks typically 120mA for

and the discharge current decreases.

7.3.9 Undervoltage Lockout (UVLO)

The undervoltage lockout prevents misoperation of the device, if the input voltage drops below the UVLO

threshold which is set to typically 2.3 V. The converter starts operation again once the input voltage exceeds the

threshold by a hysteresis of typically 200 mV.

7.3.10 Thermal Shutdown

(typical), the device goes in thermal shutdown with a hysteresis of about 10°C. Both the power FETs are turned

Start.

7.4 Device Functional Modes

7.4.1 Pulse Width Modulation (PWM) Operation

The TPSM82480 is based on a predictive OFF-time peak current control topology, operating with PWM in

continuous conduction mode for heavier loads. The switching frequency is typically 2.2MHz. Both the master and

follower phase regulate to the same VOUT level, each with a separate current loop, using the same peak current

set point, cycle by cycle. This provides excellent peak current balancing, independent of inductor dc resistance

matching. Since the follower phase operates with an adaptive delay to the master phase, phase shifted operation

is always obtained. If the load current decreases, the device runs with the master phase only (see Phase

Add/Shed and Current Balancing).

PWM only mode can be forced by pulling MODE pin High. If MODE is set Low, the device features an automatic

transition into Power Save Mode, entered at light loads, running in discontinuous conduction mode (DCM).

7.4.2 Power Save Mode (PSM) Operation

As the load current decreases to half the ripple current, the converter enters Power Save Mode operation. During

PSM, the converter operates with reduced switching frequency maintaining high conversion efficiency. Power

Save Mode is based on an adaptive peak current target, to keep output voltage ripple low. Since each pulse

takes place.

The switching frequency in PSM (one phase operation) calculates as:

space

(1)

7.4.3 Minimum Duty Cycle and 100% Mode Operation

The minimum on-time, which is typically 70ns, normally determines a limit on the minimum operating duty cycle.

The calculation is:

space

(2)

space

However, a frequency foldback lowers the switching frequency depending on the duty cycle and ensures proper

regulation for every duty cycle.