AN2798 datasheet(23/38 Pages) STMICROELECTRONICS

部件名	AN2798

功能描述	Complete DDR2/3 memory power supply

PDF	38 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

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23 / 38 page

AN2798

PM6670AS evaluation tests

23/38

8.5

VDDQ efficiency

The three working modes lead to different power efficiency. The test setup is VIN = 24 V,

FSW = 330 kHz, VDDQ = 1.8 V. The following graph summarizes the results.

8.6

VDDQ gate drivers

The PM6670 internal MOS driver turns on and off the high-side and low-side external

MOSFET, avoiding cross-conduction. In Figure 24 and 25 the gates signals are depicted

without load and with load.

Figure 24.

Forced PWM (blue), non-audible pulse-skip (green), pulse-skip (red) VDDQ efficiency

vs. output current

100

0.001

0.010

0.100

1.000

10.000

Current [A]

Forced PWM

Pulse Skip

Non Audible PS

100

0.001

0.010

0.100

1.000

10.000

Current [A]

Forced PWM

Pulse Skip

Non Audible PS

Figure 25.

External MOS gate signals (VIN = 24 V, LOAD = 0 A) (pulse-skip mode)

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