PM6680 STMicroelectronics, PM6680 Datasheet - Page 35

• Manufacturer Part Number: PM6680
• Description: IC CTRLR DUAL STEP DOWN 32VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6680

• Applications: Controller, Notebook Power System
• Voltage - Input: 6 ~ 28 V
• Number Of Outputs: 2
• Voltage - Output: 0.9 ~ 5.5 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• Output Voltage: 5 V, 0.9 V to 5.5 V, 0.9 V to 3.3 V
• Output Current: 0.33 A
• Input Voltage: 5.5 V to 28 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 10 C
• 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

PM6680
7.13.5
Power MOSFETs
Logic-level MOSFETs are recommended, since low side and high side gate drivers are
powered by LDO5. Their breakdown voltage VBR
In notebook applications, power management efficiency is a high level requirement. The
power dissipation on the power switches becomes an important factor in switching
selections. Losses of high-side and low-side MOSFETs depend on their working conditions.
The power dissipation of the high-side MOSFET is given by:
Equation 18
Maximum conduction losses are approximately:
Equation 19
where R
are approximately:
Equation 20
where ton and toff are the switching times of the turn off and turn off phases of the MOSFET.
As general rule, high side MOSFETs with low gate charge are recommended, in order to
minimize driver losses. Below there is a list of possible choices for the high side MOSFET.
Table 13.
The power dissipation of the low side MOSFET is given by:
Equation 21
Maximum conduction losses occur at the maximum input voltage:
Manufacturer
P
switching
DSon
ST
ST
High side MOSFET manufacturer
is the drain-source on resistance of the high side MOSFET. Switching losses
=
V
IN
×
I (
LOAD
STS12NH3LL
STS17NH3LL
P
conduction
(max)
Type
P
DHighSide
2
−
P
=
∆
2
DLowSide
I
R
L
DSon
)
=
×
P
t
on
conduction
×
Gate charge (nC)
×
=
V
V
f
P
IN
sw
OUT
conduction
min
DSS
+
10
18
+
×
V
P
IN
I
must be higher than V
LOAD
switching
×
I (
LOAD
(max)
(max)
2
Rated reverse voltage (V)
2
+
∆
Device description
2
I
L
)
×
INmax
30
30
t
off
×
.
f
sw
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