ADP1614-650-EVALZ Analog Devices, ADP1614-650-EVALZ Datasheet - Page 14

• Manufacturer Part Number: ADP1614-650-EVALZ
• Description: Power Management IC Development Tools Eval Board 650 kHz Switching Freq
• Manufacturer: Analog Devices
• Type: DC/DC Converters, Regulators & Controllersr
• Series: ADP1614r

Specifications of ADP1614-650-EVALZ

• Rohs: yes
• Tool Is For Evaluation Of: ADP1614
• Input Voltage: 2.5 V to 5.5 V
• Factory Pack Quantity: 1

ADP1614
To determine the crossover frequency, it is important to note that
at the crossover frequency the compensation impedance (Z
is dominated by a resistor, and the output impedance (Z
dominated by the impedance of an output capacitor. Therefore,
when solving for the crossover frequency, the equation (by defi-
nition of the crossover frequency) is simplified to
where:
R
f
Solve for R
where:
V
G
G
Therefore,
After the compensation resistor is known, set the zero formed
by the compensation capacitor and resistor to one-fourth of the
crossover frequency, or
where C
C
COMP
FB
MEA
CS
is the crossover frequency.
= 1.245 V.
= 7 A/V.
C
R
= 150 µA/V.
R
2
A
is the compensation resistor.
π
COMP
COMP
COMP
VL
COMP
×
=
f
COMP
FB
C
=
=
=
1
V
is the compensation capacitor.
V
×
V
OUT
2
4806
π
2
BG
FB
C
π
V
as follows:
Figure 27. Compensation Components
×
OUT
×
FB
f
×
C
f
×
×
C
V
AMPLIFIER
V
×
=
V
2
ERROR
OUT
f
×
IN
C
R
1
IN
C
g
COMP
×
m
OUT
×
V
×
C
G
IN
G
OUT
MEA
×
MEA
COMP
(
V
×
1
×
OUT
(
×
V
G
R
OUT
CS
)
COMP
2
R
)
C
COMP
2
COMP
×
G
CS
C2
×
OUT
) is
COMP
(15)
(16)
(17)
(18)
Rev. 0 | Page 14 of 16
)
Capacitor C2 is chosen to cancel the zero introduced by the ESR
of the output capacitor.
Solve for C2 as follows:
If a low ESR, ceramic output capacitor is used for C
optional. For optimal transient performance, R
might need to be adjusted by observing the load transient response
of the ADP1614. For most applications, the compensation resistor
should be within the range of 1 kΩ to 100 kΩ, and the compen-
sation capacitor should be within the range of 100 pF to 10 nF.
SOFT START CAPACITOR
Upon startup (EN ≥ 1.6 V) or fault recovery, the voltage at SS
ramps up slowly by charging the soft start capacitor (C
an internal 5.5 µA current source (I
capacitor charges, it limits the peak current allowed by the part
to prevent excessive overshoot at startup. Use the following
equation to determine the necessary value of the soft start
capacitor (C
the part is at the current limit with maximum load:
where:
I
Δt is the start-up time at the current limit.
V
If the applied load does not place the part at the current limit,
the value of C
results in negligible input current overshoot at startup and,
therefore, is suitable for most applications. If an unusually large
output capacitor is used, a longer soft start period is required to
prevent input inrush current.
However, if fast startup is required, the soft start capacitor can
be reduced or removed, which allows the
quickly but with greater peak switch current.
SS
SS
= 5.5 μA (typical).
= 1.23 V (typical).
C2
C
SS
=
=
ESR
I
SS
SS
R
) for a specific overshoot and start-up time when
SS
V
COMP
×
∆
can be reduced. A 68 nF soft start capacitor
SS
C
t
OUT
SS
). As the soft start
ADP1614
Data Sheet
COMP
OUT
and C
to start
, C2 is
SS
) with
COMP
(19)
(20)