PM6680ATR STMicroelectronics, PM6680ATR Datasheet - Page 20
PM6680ATR
Manufacturer Part Number
PM6680ATR
Description
IC CTRLR DUAL STEP DOWN 32VFQFPN
Manufacturer
STMicroelectronics
Datasheet
1.PM6680ATR.pdf
(48 pages)
Specifications of PM6680ATR
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
Other names
497-6896-2
PM6680ATR
PM6680ATR
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
PM6680ATR
Manufacturer:
STMicroelectronics
Quantity:
10 000
Device description
7.2
20/48
Constant on time architecture
Figure 29
off-time constrain (350 ns typ.) is introduced to allow inductor valley current sensing on
synchronous switch. A minimum on-time (130 ns) is also introduced to assure the start-up
switching sequence.
PM6680A has a one-shot generator for each power section that turns on the high side
MOSFET when the following conditions are satisfied simultaneously: the PWM comparator
is high, the synchronous rectifier current is below the current limit threshold, and the
minimum off-time has timed out.
Once the on-time has timed out, the high side switch is turned off, while the synchronous
switch is turned on according to the anti-cross conduction circuitry management.
When the negative input voltage at the PWM comparator
down replica of the output voltage (see the external R1/R2 divider in
valley limit (determined by internal reference Vr = 0.9 V), the low-side MOSFET is turned off
according to the anti-cross conduction logic once again, and a new cycle begins.
Figure 29. Constant on-time block diagram
In steady state the FB pin voltage is about Vr and the regulated output voltage depends on
the external divider:
Equation 4
shows the simplified block diagram of a constant on time controller. A minimum
OUT
=
Vr
×
⎛
⎝
1
+
R
------ -
R
2
1
⎞
⎠
(Figure
29), which is a scaled-
Figure
29), reaches the
PM6680A