STEVAL-ISA052V1 STMicroelectronics, STEVAL-ISA052V1 Datasheet - Page 44

• Manufacturer Part Number: STEVAL-ISA052V1
• Description: KIT EVAL PM6675S HE CTLR 2A REG
• Manufacturer: STMicroelectronics

Specifications of STEVAL-ISA052V1

• Main Purpose: DC/DC, Step Down with LDO
• Outputs And Type: 2, Non-Isolated
• Voltage - Output: 1.5V, 0.6 ~ 3.3V
• Current - Output: 10A, 2A
• Voltage - Input: 4.5 ~ 28 V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: PM6675
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-8426

Application information
44/53
where R
Switching losses are approximately given by:
Equation 42
where t
gate-driver current capability and the gate charge Q
low R
As general rule, the R
MOSFET.
Logic-level MOSFETs are recommended, as long as low-side and high-side gate drivers are
powered by V
greater than the maximum input voltage V
Below some tested high-side MOSFETs are listed.
Table 14.
In buck converters the power dissipation of the synchronous MOSFET is mainly due to
conduction losses:
Equation 43
Maximum conduction losses occur at the maximum input voltage:
Equation 44
The synchronous rectifier should have the lowest R
MOSFET turns on, high d
through its gate-drain capacitance C
the choice of the low-side MOSFET is a trade-off between on resistance and gate charge; a
good selection should minimizes the ratio C
Equation 45
Below some tested low-side MOSFETs are listed.
Manufacturer
DSon
ON
P
DS(on)
ST
IR
switching
. Unfortunately low R
and t
Evaluated high-side MOSFETs
VCC
is the drain-source on-resistance of the control MOSFET.
OFF
=
= +5 V. The breakdown voltage of the MOSFETs (V
V
are the turn-on and turn-off times of the MOSFET and depend on the
IN
DS(on)
STS12NH3LL
⋅
I (
IRF7811
P
LOAD
V
Type
conduction
/d
x Q
t
(max)
of the phase node can bring up even the low-side gate
DSon
gate
2
=
−
P
product should be minimized to find the suitable
R
RRS
MOSFETs have a great gate charge.
C
DLowSide
∆
DSon
2
GS
I
L
, causing a cross-conduction problem. Once again,
)
R
=
⋅
INmax
(mΩ)
⋅
t
DS(on)
10.5
⎛
⎜
⎜
⎝
C
on
9
RSS
1
≅
ISS
−
⋅
P
f
.
sw
V
conduction
−
V
/ C
IN
OUT
C
+
,
MAX
gate
DS(on)
GS
RSS
V
IN
. A greater efficiency is achieved with
where
⎞
⎟
⎟
⎠
⋅
⋅
I (
Gate charge
I
LOAD
as possible. When the high-side
LOAD
(nC)
12
18
,
MAX
(max)
2
2
+
BRDSS
∆
2
I
L
)
⋅
Rated reverse
t
) must be
off
voltage (V)
⋅
f
sw
30
30
PM6675S