(

)

-

=

´

´

´

IN

OUT

OUT

LOAD(LL)

X

IN

SW

V

V

V

1

I

2 L

V

f

´

³

´

OUT

SW

X

V

ESR

20 mV

f

L

V

VDDQSNS

V

REFIN

(1)

(2)

t

ON

t

OFF

Slope (2)

Jitter

20 mV

Slope (1)

Jitter

UDG-10139

V

REFIN +Noise

TPS51216

SLUSAB9A – NOVEMBER 2010 – REVISED APRIL 2013

www.ti.com

Figure 31. Ripple Voltage Slope and Jitter Performance

For a good jitter performance, use the recommended down slope of approximately 20 mV per switching period as

shown in Figure 31 and Equation 2.

where

•

VOUT is the VDDQ output voltage

•

LX is the inductance

(2)

Light-Load Operation

In auto-skip mode, the TPS51216 SMPS control logic automatically reduces its switching frequency to improve

light-load efficiency. To achieve this intelligence, a zero cross detection comparator is used to prevent negative

inductor current by turning off the low-side MOSFET. Equation 3 shows the boundary load condition of this skip

mode and continuous conduction operation.

(3)

18

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