ADP3050-BL1-EVZ Analog Devices Inc, ADP3050-BL1-EVZ Datasheet - Page 14

• Manufacturer Part Number: ADP3050-BL1-EVZ
• Description: Blank ADISimPower Eval ADP3050
• Manufacturer: Analog Devices Inc

Specifications of ADP3050-BL1-EVZ

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADP3050
Table 4. Manufacturers
Inductor Manufacturers
Sumida
Coilcraft
Cooper Bussmann Coiltronics
NEC Tokin
Würth Elektronik
Toko
CATCH DIODE SELECTION
The recommended catch diode is a Type 1N5818 Schottky or
equivalent. The low forward voltage drop (450 mV typical at
1 A) and fast switching speed of a Schottky rectifier provide the
best performance and efficiency. The 1N5818 is rated at 30 V
reverse voltage and 1 A average forward current. For lower
input voltages, use a lower voltage Schottky to reduce the diode
forward voltage drop and increase overall system efficiency; for
example, a 12 V to 5 V system does not need a 30 V diode. For
automotive applications, a 60 V Schottky may be necessary. The
average forward current for the catch diode is calculated by
For the earlier continuous mode example (12 V to 5 V at
800 mA), the average diode current is
For this system, a 1N5817 is a good choice (rated at 20 V and 1 A).
Do not use catch diodes rated less than 1 A. Even though the
average current can be less than 1 A under normal operating
conditions, as the diode current is much higher under fault
conditions. The worst-case fault condition for the diode occurs
when the regulator becomes slightly overloaded (sometimes
called a soft short). This is usually only a problem when the
input voltage to output voltage ratio is greater than 2.5. Under
this condition, the load current needed is slightly more than the
regulator can provide. The output voltage droops slightly, and
the switch stays on every cycle until the internal current limit is
reached. Under this condition, the load current can reach
around 1.2 A. For example, when using a system with an input
voltage of 24 V and an output voltage of 5 V, if a gradual overload
causes the output voltage to droop to 4 V, the average diode
current is
I
I
I
DIODE
DIODE
DIODE
(
(
(
AVG
AVG
AVG
)
)
)
=
=
=
0
1
I
2 .
OUT
8 .
×
×
12
24
×
12
24
V
−
−
IN
5
4
V
=
−
=
IN
V
. 0
1
0 .
OUT
47
A
A
Capacitor Manufacturers
AVX
Kemet
Murata
Nemco
Vishay Sprague
NEC Tokin
Taiyo Yuden
Rev. B | Page 14 of 24
(5)
(6)
(7)
If the system must survive such gradual overloads for a prolonged
period of time, ensure the diode chosen can survive these
conditions. A larger 2 A or 3 A diode can be used if necessary.
Choosing a Catch Diode
Use the following steps to pick an appropriate catch diode.
Table 5 shows several Schottky rectifiers with different reverse
voltage and forward current ratings.
The average diode current rating must be sufficient to provide
the required load current (see the calculations in the previous
section). Diodes rated below 1 A should not be used, even if the
average diode current is much lower.
The reverse voltage rating of the catch diode should be at least the
maximum input voltage. Often a higher rating is chosen
(1.2× the maximum input voltage) to provide a safety margin.
Table 5. Schottky Diode Selection Guide
V
15 V
20 V
30 V
40 V
INPUT CAPACITOR SELECTION
The input bypass capacitor plays an important role in proper
regulator operation, minimizing voltage transients at the input
and providing a short local loop for the switching current. Place
this capacitor close to the ADP3050 between the IN and GND
pins using short, wide traces. This input capacitor should have
an rms ripple current rating of at least
This rating is crucial because the input capacitor must be able to
withstand the large current pulses present at the input of a step-
down regulator. Values of 20 μF to 50 μF are typical, but the
main criteria for capacitor selection is the ripple current and
voltage ratings.
R
I
CIN
(
RMS
)
≥
I
1 A
10BQ15
1N5817
V1N5818
1N5819
OUT
Schottky Diode Manufacturers
Motorola
Diodes, Inc.
International Rectifier
Nihon Inter Electronics
×
V
V
OUT
IN
−
⎛
⎜
⎜
⎝
V
2 A
30BQ15
B220
B230
B240
V
OUT
IN
⎞
⎟
⎟
⎠
2
3 A
SK32
SK33
SK34
(8)