PM6680A STMicroelectronics, PM6680A Datasheet - Page 22

• Manufacturer Part Number: PM6680A
• Description: IC CTLR DUAL SYNC STDN 5X5VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6680A

• Applications: Controller, Embedded Computer System
• Voltage - Input: 6 ~ 36 V
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• For Use With: 497-6379 - BOARD EVALUATION FOR PM6680A497-6378 - BOARD EVALUATION FOR PM6680497-6425 - BOARD EVAL BASED ON PM6680A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Device description
7.4
22/48
Pulse skip mode
If the SKIP pin is tied to ground, the device works in skip mode.
At light loads a zero-crossing comparator truncates the low-side switch on-time when the
inductor current becomes negative. In this condition the section works in discontinuous
conduction mode. The threshold between continuous and discontinuous conduction mode
is:
Equation 5
For higher loads the inductor current doesn’t cross the zero and the device works in the
same way as in PWM mode and the frequency is fixed to the nominal value.
Figure 31.
Figure 31
average inductor current equal to load current, in SKIP mode some switching cycles are
skipped. When the output ripple reaches the regulated voltage Vreg, a new cycle begins.
The off cycle duration and the switching frequency depend on the load condition.
As a result of the control technique, losses are reduced at light loads, improving the system
efficiency.
shows inductor current waveforms in PWM and SKIP mode. In order to keep
PWM and pulse skip mode inductor current
ILOAD SKIP
(
)
=
V
----------------------------- -
IN
2
–
×
V
L
OUT
×
T
ON
PM6680A