ADP2303ARDZ-R7 Analog Devices Inc, ADP2303ARDZ-R7 Datasheet - Page 20

• Manufacturer Part Number: ADP2303ARDZ-R7
• Description: IC REG SW STPDWN NONSYNCH 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Step-Down (Buck), PFM/PWM - Current Moder

Specifications of ADP2303ARDZ-R7

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adj to 0.8V
• Current - Output: 3A
• Frequency - Switching: 700kHz
• Voltage - Input: 3 V ~ 20 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width) Exposed Pad
• Primary Input Voltage: 20V
• No. Of Outputs: 1
• Output Current: 3A
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 3 - 168 Hours
• Peak Reflow Compatible (260 C): Yes
• Leaded Process Compatible: Yes
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ADP2303ARDZ-R7; ADP2303ARDZ-R7TR

DESIGN EXAMPLE
This section provides the procedures to select the external compo-
nents, based on the example specifications listed in Table 10.
The schematic for this design example is shown in Figure 51.
Because the output current is 3 A, the ADP2303 is chosen for
this application.
Table 10. Step-Down DC-to-DC Regulator Requirements
Parameter
Input Voltage, V
Output Voltage, V
Programmable
PGOOD
CATCH DIODE SELECTION
Select the catch diode. A Schottky diode is recommended for best
efficiency because it has a low forward voltage drop and faster
switching speed. The average current of the catch diode in
normal operation, with a typical Schottky diode forward
voltage, can be calculated using the following equation:
where:
V
V
I
V
Therefore, I
In this case, selecting a SSB43L, 4.0 A, 30 V surface-mount
Schottky diode results in more reliable operation.
INDUCTOR SELECTION
Select the inductor by using the following equation:
where:
V
V
I
V
f
This results in L = 4.12 μH. The closest standard value is 4.7 μH;
therefore, ΔI
ADP2302/ADP2303
SW
LOAD(max)
LOAD(max)
OUT
IN
D
OUT
IN
D
UVLO Voltage
= 0.4 V.
= 0.4 V.
= 700 kHz.
= 12 V.
= 12 V.
= 3.3 V.
= 3.3 V.
I
L
DIODE
=
= 3 A.
= 3 A.
0
3 .
(
DIODE(AVG)
AVG
×
RIPPLE
(
V
I
)
IN
IN
LOAD
OUT
=
= 0.7 A.
−
⎛
⎜
⎜
⎝
1
V
(max)
= 2.1 A.
−
OUT
Specification
12.0 V ± 10%
3.3 V, 3 A, 1% V
at full load condition
V
approximately 7.8 V
Not used
V
V
IN
×
OUT
)
IN
start-up voltage
f
sw
+
+
V
×
V
D
⎛
⎜
⎜
⎝
D
V
V
⎞
× ⎟ ⎟
⎠
OUT
IN
OUT
I
+
LOAD
+
V
ripple
V
D
D
(max)
⎞
⎟
⎟
⎠
Additional
Requirements
None
None
None
None
Rev. 0 | Page 20 of 28
The inductor peak current is calculated using the following
equation:
where:
I
ΔI
The calculated peak current for the inductor is 3.4 A. Therefore,
in this application, select VLF10040T-4R7N5R4 as the inductor.
OUTPUT CAPACITOR SELECTION
Select the output capacitor based on the minimum output
voltage ripple requirement, according to the following equation:
where:
ΔI
f
ΔV
If ESR of the ceramic capacitor is 3 mΩ, then C
Because the output capacitor is one of two external components
that control the loop stability and according to the recommended
external components in Table 11, choose two 47 μF capacitor
with a 6.3 V voltage rating in this application.
RESISTIVE VOLTAGE DIVIDER SELECTION
The output feedback resistive voltage divider is
For the 3.3 V output voltage, choose R
R
according to the recommended values in Table 11.
The resistive voltage divider for the programmable V
voltage is
If V
R
SW
LOAD(max)
BOT
EN1
RIPPLE
RIPPLE
= 700 kHz.
RIPPLE
STARTUP
, which, in this case, is 56 kΩ.
V
= 10.2 kΩ as the feedback resistive voltage divider
V
I
Δ
PEAK
V
OUT
STARTUP
= 0.7 A.
= 0.7 A.
= 33 mV (1% of output voltage).
RIPPLE
= 3 A.
= 7.8 V, choose R
=
=
. 0
I
=
LOAD
=
800
⎛
⎜
⎜
⎝
Δ
1
R
I
(max)
2 .
V
RIPPLE
EN2
×
V
⎛
⎜
⎜
⎝
+
1
+
×
+
1
Δ
⎛
⎜
⎜
⎝
2 .
I
R
R
EN2
8
RIPPLE
μA
2
TOP
BOT
×
= 10.2 kΩ, and then calculate
f
⎞
⎟
⎟
⎠
sw
⎞
⎟
⎟
⎠
×
1
×
R
C
EN1
OUT
TOP
+
= 31.6 kΩ and
1
+
2 .
ESR
V
OUT
C
OUT
= 4 μF.
IN
⎞
⎟
⎟
⎠
start-up