XRP7675EVB Exar, XRP7675EVB Datasheet - Page 7

• 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

THEORY OF OPERATION
F
The XRP7675 is a synchronous, current-mode,
step-down regulator with light-load efficiency.
The
monitoring the current through M2 and turning
it off when current drops below 0A. The
XRP7675 regulates input voltages from 4.5V to
18V and supplies up to 3A of load current. It
uses current-mode control to regulate the
output
measured at FB through a resistive voltage
divider and input to a transconductance error
amplifier. The high-side switch current is
compared to the output of the error amplifier
to control the output voltage. The regulator
utilizes internal N-channel MOSFETs to step-
down
capacitor connected between BS and SW acts
as a supply for high-side MOSFET. This
capacitor is charged from the internal 5V
supply when SW node is low. The XRP7675
has
including OCP, OVP, OTP, UVLO and output
short-circuit.
PROGRAMMABLE SOFT
The soft-start time is fully programmable via
CSS capacitor, placed between the SS and
GND pin. The CSS is charged by a 5µA
constant-current source, generating a ramp
signal fed into non-inverting input of the error
amplifier. This ramp regulates the voltage on
comp pin during the regulator startup, thus
realizing soft-start. Calculate the required CSS
from:
Where:
tss is the required soft-start time
V
Please note that the above is a simplified
equation and will provide an approximate CSS
value. For a required soft-start, a more
accurate CSS can be determined based on
empirical data.
© 2013 Exar Corporation
FB
UNCTIONAL
is the feedback voltage (0.925V nominal)
several
light-load
the input voltage. A bootstrapping
voltage.
D
powerful
ESCRIPTION
efficiency
The
-
START
output
protection
3
3
is
A
A
1
1
achieved
8
8
voltage
V
V
S
S
features
y
y
n
n
c
c
by
h
h
is
r
r
o
o
7/12
n
n
o
o
u
u
OVERCURRENT PROTECTION AND HICCUP
MODE
The OCP protects against accidental increase
in load current or a short circuit. The current
of internal switch M1 is monitored. If this
current exceeds 5.6A typical then a hiccup
mode is triggered. In hiccup mode, internal
power FETs are turned off and the SS pin is
discharged. When SS reaches 0.2V a softstart
is initiated. The regulator will stay in hiccup
mode until overcurrent is removed. Note that
when the soft start pin is below approximately
0.5V the regulator switching frequency is
90kHz.
OVERVOLTAGE PROTECTION OVP
The XRP7675 has internal OVP. When V
exceeds the OVP threshold (when V
1.1V) the power switching will be turned off.
The XRP7675 will restart when overvoltage
condition is removed.
OVER
If the junction temperature exceeds 160°C the
OTP circuit is triggered, turning off the internal
control circuit and switched M1 and M2. When
junction temperature drops below 140°C the
XRP7675 will restart.
s
s
P
P
F
-
F
TEMPERATURE PROTECTION OTP
M
M
/
/
P
P
W
W
M
M
S
S
t
t
e
e
p
p
-
-
D
D
o
o
w
w
n
n
X
X
R
R
R
R
e
e
FB
P
P
g
g
Rev. 1.0.0
u
u
exceeds
7
7
l
l
6
6
a
a
7
t
7
t
o
OUT
o
5
5
r
r