RT8258
Table 1. Recommended Component Selection
V
OUT
R1 (kΩ)
R2 (kΩ)
L (μH)
C
OUT
(μF)
1.2V
100
200
3.6
22
1.5V
91
100
3.6
22
1.8V
91
75
4.7
22
2.5V
100
47
6.8
22
3.3V
100
32.4
10
22
5V
91
17.4
15
22
8V
91
10
22
22
10V
91
7.87
22
22
15V
120
6.8
33
22
Note : The value of R1 is related to the loop bandwidth of the RT8258. It is strongly recommended to follow the
parameters in above table for the specific output voltage.
Function Block Diagram
VIN
1µA
Regulator
10k
3V
1.1V
-
EN
+
Shutdown Reference
Comparator
深
圳
市
+
EA
-
Ramp
Generator
Oscillator
700kHz
富
�½�
Current Sense Amp
维
+
-
电
S
子
-
+
X20
FB
GND
Functional Pin Description
Pin No.
1
2
3
4
5
6
Pin Name
BOOT
GND
FB
5
7
0
深
-
5
3
2
1
8
400k
30pF
5
5
5
2
8
/
R
1
2
3
Q
Driver
0
5
4
4
25mΩ
BOOT
PHASE
PWM
Comparator
OC Limit Clamp
1pF
圳
Gate Driver Bootstrap Input Pin. Connect a 10nF or greater capacitor between PHASE
and BOOT pins to supply the MOSFET driver.
Ground Pin. This pin should be connected to the (-) terminal of the output capacitor and
it should be kept away from the D1 and input capacitor for noise prevention.
Output Voltage Feedback Input Pin. An external resistor divider from the output to GND
tapped to the FB pin sets the output voltage. The value of the divider resistors also set
loop bandwidth.
Chip Enable (Active High). If the EN pin is open, it will be pulled to high by internal
circuit.
Power Supply Input Pin. Bypass VIN to GND with a suitable large capacitor to prevent
large voltage spikes from appearing at the input.
市
鼎
�½
诚
际
大
厦
2
Bootstrap
Control
室
5
0
8
Pin Function
EN
VIN
PHASE
Power Switching Output Pin. Connect this pin to the output inductor.
www.richtek.com
2
DS8258-02 March 2011
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
