RT8270 RICHTEK [Richtek Technology Corporation], RT8270 Datasheet - Page 2

• Manufacturer Part Number: RT8270
• Description: 2A, 22V, 1.2MHz Step-Down Converter
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT8270
Table 1. Recommended Component Selection
Functional Pin Description
Function Block Diagram
www.richtek.com
2
V
Pin No.
OUT
1.222
3.3
2.5
1.8
12
VIN
5
1
2
3
4
5
6
7
8
EN
(V)
BOOT
VIN
SW
GND
FB
COMP
EN
NC
1µA
R1 (kΩ)
10k
Pin Name
10.45
88.7
4.75
3V
30
17
0
V
CC
1V
Comparator
Shutdown
R2 (kΩ)
VA V
Regulator
-
+
High Side Gate Drive Boost Input. BOOT supplies the drive for the high side N-MOSFET
switch. Connect a 10nF or greater capacitor from SW to BOOT to power the high side
switch.
Power Input. V
switches. Bypass VIN to GND with a suitable large capacitor to eliminate noise on the
input to the IC.
Power Switching Output. SW is the switching node that supplies power to the output.
Connect the output LC filter from SW to the output load. Note that a capacitor is required
from SW to BOOT to power the high side switch.
Ground.
Feedback Input. FB senses the output voltage to regulate said voltage. The feedback
reference voltage is 1.222V typically.
Compensation Node. COMP is used to compensate the regulation control loop.
Connect a series RC network from COMP to GND to compensate the regulation control
loop. In some cases, an additional capacitor from COMP to GND is required.
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN higher than
1.4V to turn on the regulator, lower than 0.4V to turn it off. If the EN pin is open, it will be
pulled to high by internal circuit.
No Internal Connection.
Internal
10
10
10
10
10
10
CC
FB
R
0.6V
1.222V
Gm = 780µA/V
C
23.1
9.1
51
18
12
10
(kΩ)
Comparator
IN
UV
+
-
1.2MHz/440kHz
Foldback
supplies the power to the IC, as well as the step-down converter
Control
+
-
Oscillator
C
EA
C
0.86
1.2
1.8
2.2
2.2
2.2
(nF)
COMP
L1 (μH)
6.8
4.7
4.7
2.2
2.2
10
Comparator
Current
+
-
Pin Function
Slope Comp
C
OUT
Logic
22
22
22
22
22
22
Current Sense
(μF)
Amplifier
+
-
DS8270-01 March 2011
VA
BOOT
SW
GND