RT8259 RICHTEK [Richtek Technology Corporation], RT8259 Datasheet - Page 2

• Manufacturer Part Number: RT8259
• Description: 1.2A, 24V, 1.4MHz Step-Down Converter
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT8259
Table 1. Recommended Component Selection, C2 = 22μ μ μ μ μ F
Functional Pin Description
Function Block Diagram
www.richtek.com
2
V
R1 (kΩ)
R2 (kΩ)
L1 (μH)
Pin No.
OUT
1
2
3
4
5
6
(V)
GND
VIN
EN
FB
Pin Name
BOOT
GND
FB
EN
VIN
PHASE
124
1.2
62
2
10k
3V
1µA
49.9
1.8
62
2
Bootstrap. A capacitor is connected between PHASE and BOOT pins to form a floating
supply across the power switch driver. This capacitor is needed to drive the power switch‘s
gate above the supply voltage.
Ground. This pin is the voltage reference for the regulated output voltage. For this reason,
care must be taken in its layout. This node should be placed outside of the D1 to C1 ground
path to prevent switching current spikes from inducing voltage noise into the part.
Feedback. 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.
Supply Voltage. Bypass VIN to GND with a suitable large capacitor to prevent large voltage
spikes from appearing at the input.
Switch Output.
1.1V
Comparator
Shutdown
29.4
2.5
3.6
62
+
-
Reference
Regulator
19.6
3.3
4.7
62
400k
6.8
62
12
+
-
1pF
5
Generator
EA
Oscillator
1.4MHz
30pF
Ramp
7.5
10
68
8
5.9
10
10
68
Pin Function
OC Limit Clamp
Comparator
Current Sense Amp
+
-
PWM
3.9
15
15
68
S
R
Q
X20
Bootstrap
Control
Driver
+
-
25mΩ Ω
DS8259-03 March 2011
BOOT
PHASE