ADP1621ARMZ-R7 Analog Devices Inc, ADP1621ARMZ-R7 Datasheet - Page 15

• Manufacturer Part Number: ADP1621ARMZ-R7
• Description: IC CTRLR DC/DC PWM STEPUP 10MSOP
• Manufacturer: Analog Devices Inc
• Type: Step-Up (Boost)r

Specifications of ADP1621ARMZ-R7

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Current - Output: 1A
• Frequency - Switching: 100kHz ~ 1.5MHz
• Voltage - Input: 2.9 ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Primary Input Voltage: 5.5V
• No. Of Outputs: 1
• Output Current: 1A
• No. Of Pins: 10
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Frequency Max: 1.5MHz
• Termination Type: SMD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: ADP1621-EVALZ - BOARD EVALUATION FOR ADP1621
• Voltage - Output: -
• Power - Output: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: ADP1621ARMZ-R7; ADP1621ARMZ-R7TR

INPUT CAPACITOR SELECTION
The bulk input capacitor provides a low impedance path for the
inductor ripple current. Capacitor C1 in Figure 1 represents a
bulk input capacitor. Choose a bulk input capacitor whose
impedance at the switching frequency is lower than the
impedance of the voltage source V
The preferred bulk input capacitor is a 10 μF to 100 μF ceramic
capacitor because it has low equivalent series resistance (ESR) and
low impedance. Aluminum electrolytic and aluminum polymer
capacitors can also be used as the bulk input capacitors. The bulk
input capacitor does not need to be placed very close to the IN
and PIN pins. Aluminum electrolytic capacitors are the cheapest
and generally have high ESR values, which increase dramatically at
temperatures less than 0°C. Some aluminum electrolytic capacitors
have ESR less than 20 mΩ, but their capacitances are generally
greater than 800 μF. Aluminum polymer capacitors are more
expensive than the aluminum electrolytic ones, but are generally
cheaper than the ceramic capacitors for the same amount of
capacitance. Polymer capacitors have relatively low ESR, with
some models having less than 10 mΩ.
Regardless of the type of capacitor used, make sure the ripple
current rating of the bulk input capacitor, I
where ΔI
In addition to the bulk input capacitor, a bypass input capacitor is
required. The function of the bypass capacitor is to locally filter the
input voltage to the ADP1621 and maintain the input voltage at a
steady value during switching transitions. The bypass capacitor is
typically a 0.1 μF or greater ceramic capacitor and should be placed
as close as possible to the IN and PIN pins of the ADP1621.
Capacitors C3 and C4 in Figure 1 represent the bypass capacitors.
OUTPUT CAPACITOR SELECTION
The output capacitor maintains the output voltage and supplies
current to the load while the external MOSFET is on.
The value and characteristics of the output capacitor greatly
affect the output voltage ripple and stability of the converter.
I
CIN
,
L
RMS
is the peak-to-peak inductor ripple current.
=
1
3
×
Δ
2
I
L
IN
.
CIN,RMS
, is greater than
(11)
Rev. A | Page 15 of 32
The amount of peak-to-peak output voltage ripple, ΔV
be approximated by
where ΔI
switching frequency, C
effective ESR of C
inductance of C
Because the output capacitor is typically greater than 40 μF, the
ESR dominates the output capacitance impedance and thus the
output voltage ripple. The use of low ESR, ceramic dielectric
capacitors is preferred, although aluminum electrolytic,
tantalum, OS-CON™ (from Sanyo), and aluminum polymer
capacitors can be used. At higher switching frequencies, the ESL
of the output capacitor may also be a factor in determining the
output voltage ripple. Multiple capacitors can be connected in
parallel to reduce the effective ESR and ESL. Keep in mind that
the capacitance of a given capacitor typically degrades with
increased temperature and bias voltage. Consult the capacitor
manufacturer’s data sheet when determining the actual
capacitance of a capacitor under certain conditions.
Ensure that the output capacitor ripple current rating, I
is greater than
DIODE SELECTION
The diode conducts the inductor current to the output capacitor
and load while the MOSFET is off. The average diode current is
the load current:
The rms diode current in continuous conduction mode is given by
where D is the duty cycle.
The power dissipated in the diode is
where V
Δ
I
I
I
P
COUT
DIODE
DIODE
DIODE
V
D
OUT
L
is the forward-voltage drop of the diode.
⎛
⎜
⎜
⎝
is the peak-to-peak inductor ripple current, f
,
RMS
,
,
RMS
2
AVE
=
≈
π
V
⎛
⎜
⎝
×
=
=
=
D
OUT
I
1
f
I
LOAD
I
×
SW
OUT
I
1
−
LOAD
LOAD
LOAD
.
1
−
I
D
LOAD
×
, and ESL is the effective equivalent series
D
C
+
OUT
×
×
OUT
Δ
2
is the output capacitance, ESR is the
1
I
1
L
−
D
⎞
⎟
⎟
⎠
−
⎞
× ⎟
⎠
2
D
D
+
ESR
2
+
(
2
π
×
f
SW
ADP1621
×
ESL
OUT
SW
COUT,RMS
)
2
, can
is the
(12)
(13)
(14)
(15)
(16)
,