B1077AS-4R7N AD [Analog Devices], B1077AS-4R7N Datasheet - Page 22

• Manufacturer Part Number: B1077AS-4R7N
• Description: 1.2 A, 20 V, 700 kHz/1.4 MHz, Nonsynchronous Step-Down Regulator
• Manufacturer: AD [Analog Devices]

ADP2300/ADP2301
RESISTIVE VOLTAGE DIVIDER SELECTION
To select the appropriate resistive voltage divider, first calculate the
output feedback resistive voltage divider, and then calculate the
resistive voltage divider for the programmable V
The output feedback resistive voltage divider is
For the 3.3 V output voltage, choose R
= 10.2 kΩ as the feedback resistive voltage divider, according to
the recommended values in Table 11.
Table 11. Recommended External Components for Typical Applications at 1.2 A Output Load
Part Number
ADP2300 (700 kHz)
ADP2301 (1.4 MHz)
V
OUT
=
. 0
800
V
×
⎛
⎜
⎜
⎝
1
+
V
18
18
12
12
12
12
12
9
9
5
5
18
18
12
12
12
9
9
5
5
R
R
IN
FB
FB
(V)
1
2
⎞
⎟
⎟
⎠
10µF
25V
C1
V
IN
= 12V
FB1
V
3.3
5.0
1.2
1.8
2.5
3.3
5.0
3.3
5.0
1.8
2.5
3.3
5.0
2.5
3.3
5.0
3.3
5.0
1.8
2.5
OUT
10.2kΩ
= 31.6 kΩ and R
56kΩ
1%
1%
R3
R4
(V)
IN
start-up voltage.
Figure 48. Schematic for the Design Example
VIN
EN
I
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
OUT
FB2
ADP2301
(1.4MHz)
(A)
Rev. 0 | Page 22 of 28
GND
L (μH)
10
15
6.8
6.8
10
10
10
10
10
4.7
4.7
4.7
6.8
4.7
4.7
4.7
4.7
4.7
2.2
2.2
BST
SW
FB
The resistive voltage divider for the programmable V
voltage is
If V
R
EN1
STARTUP
C3
0.1µF
6.3V
, which in this case is 56 kΩ.
D1
B230A
V
C
22
22
2 × 22
2 × 22
22
22
22
22
22
2 × 22
22
22
10
22
22
10
22
10
2 × 22
22
STARTUP
OUT
4.7µH
2.0A
L1
= 7.8 V, choose R
(μF)
31.6kΩ
10.2kΩ
=
1%
1%
R1
R2
⎛
⎜
⎜
⎝
1
R
2 .
R
31.6
52.3
4.99
12.7
21.5
31.6
52.3
31.6
52.3
12.7
21.5
31.6
52.3
21.5
31.6
52.3
31.6
52.3
12.7
21.5
EN
V
FB1
V
OUT
2
1.2A
+
(kΩ), ±1%
= 3.3V
1
C2
22µF
6.3V
2 .
EN2
μA
= 10.2 kΩ, and then calculate
⎞
× ⎟ ⎟
⎠
R
EN
1
+
1
R
10.2
10
10
10.2
10.2
10.2
10
10.2
10
10.2
10.2
10.2
10
10.2
10.2
10
10.2
10
10.2
10.2
2 .
FB2
V
(kΩ), ±1%
IN
start-up