XRP7675EVB Exar, XRP7675EVB Datasheet - Page 9

• Manufacturer Part Number: XRP7675EVB
• Description: Power Management IC Development Tools 3A 18V PFM/PWM EVAL Board
• Manufacturer: Exar
• Type: DC/DC Converters, Regulators & Controllersr

Specifications of XRP7675EVB

• Product: Evaluation Boards
• Tool Is For Evaluation Of: XRP7675
• Input Voltage: 4.5 V to 18 V
• Output Voltage: 0.925 V to 16 V
• Description/function: Evaluation board for the XRP7675
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Output Current: 3
• For Use With: XRP7675

because of their low ESR which is typically in
the range of 5mΩ. Therefore ΔV
capacitive. For ceramic capacitors calculate
the ΔV
Where:
ΔI
C
f
If tantalum or electrolytic capacitors are used
then ΔV
INPUT CAPACITOR C
Select the input capacitor for voltage rating,
RMS current rating and capacitance. The
voltage rating should be at least 50% higher
than the regulator’s maximum input voltage.
Calculate the capacitor’s current rating from:
Where:
I
D is duty cycle (D=V
Calculate the C
Where:
ΔV
nominally set at 1% of V
O
An optional Schottky diode may be paralleled
between the GND pin and SW pin to improve
the regulator efficiency. See Table 3.
© 2013 Exar Corporation
s
OUT
OUT
PTIONAL
is nominal switching frequency (340kHz)
L
IN
Part Number
is from table 1 or 2 in previous section
is regulator’s maximum current (2A)
is the value calculated above
MBRS130
is the permissible input voltage ripple,
OUT
SK13
B130
OUT
from:
Table 3: Optional Schottky diode
is essentially a function of ESR:
S
CHOTTKY DIODE
IN
Voltage/Current
capacitance from:
30V/1A
30V/1A
30V/1A
Rating
IN
OUT
/V
IN
IN
)
3
3
A
A
International
1
1
Diodes, Inc.
Diodes, Inc.
OUT
8
Rectifier
8
Vendor
V
V
is mainly
S
S
y
y
n
n
c
c
h
h
r
r
o
o
9/12
n
n
o
o
u
u
EXTERNAL BOOTSTRAP DIODE
A low-cost diode, such as 1N4148, may
provide
voltage is 5V or the output is 5V or 3.3V.
Circuit configuration is shown in figures 16 and
17. The external bootstrap diode is also
recommended where duty cycle (V
larger than 65%.
LOOP COMPENSATION
XRP7675 utilizes current-mode control. This
allows
components to compensate the regulator. In
general only two components are needed: RC
and CC. Proper compensation of the regulator
(determining RC and CC) results in optimum
transient response. In terms of power supply
control theory, the goals of compensation are
to choose RC and CC such that the regulator
loop
between 15kHz and 34kHz. The corresponding
phase-margin should be between 45 degrees
and 65 degrees. An important characteristic of
current-mode buck regulator is its dominant
pole. The frequency of the dominant pole is
given by:
s
s
V
IN
P
P
= 5V
F
F
XRP7675
gain
Fig. 16: Optional external bootstrap diode
Fig. 17: Optional external bootstrap diode
M
M
using
/
/
higher
where output voltage is 5V or 3.3V
P
P
where input voltage is fixed 5V
W
W
has
M
M
SW
BS
a
efficiency
S
IN
a
S
t
t
XRP7675
e
e
minimum
crossover
p
p
-
-
10nF
D
D
1N4148
o
o
w
w
when
SW
BS
n
n
X
X
frequency
R
of
R
R
R
e
e
the
OUT
V
P
P
g
g
or 3.3V
Rev. 1.0.0
OUT
C
1N4148
external
u
u
7
7
OUT
/V
10nF
= 5V
l
l
6
6
a
a
IN
input
7
t
7
t
) is
o
o
5
5
fc
r
r