RT8258 RICHTEK [Richtek Technology Corporation], RT8258 Datasheet - Page 2

• Manufacturer Part Number: RT8258
• Description: 1.2A, 24V, 700kHz Step-Down Converter
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT8258
Table 1. Recommended Component Selection
Function Block Diagram
Functional Pin Description
www.richtek.com
2
C
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.
R1 (kΩ)
R2 (kΩ)
L (μH)
OUT
Pin No.
V
OUT
1
2
3
4
5
6
(μF)
GND
VIN
EN
FB
1.2V
BOOT
GND
FB
EN
VIN
PHASE
100
200
Pin Name
3.6
22
10k
3V
1µA
1.5V
1.1V
100
3.6
91
22
Comparator
Shutdown
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.
Power Switching Output Pin. Connect this pin to the output inductor.
+
-
1.8V
4.7
91
75
22
Reference
Regulator
2.5V
400k
100
6.8
47
22
+
-
1pF
Generator
EA
Oscillator
700kHz
30pF
Ramp
3.3V
32.4
100
10
22
OC Limit Clamp
17.4
Comparator
5V
91
15
22
Current Sense Amp
Pin Function
+
-
PWM
S
R
8V
91
10
22
22
Q
X20
Bootstrap
Control
Driver
+
7.87
-
10V
91
22
22
25mΩ
15V
120
DS8258-02 March 2011
6.8
33
22
BOOT
PHASE