rt8070 Richtek Technology Corporation, rt8070 Datasheet - Page 2

• Manufacturer Part Number: rt8070
• Description: 4a, 2mhz, Synchronous Step-down Converter
• Manufacturer: Richtek Technology Corporation

RT8070
Typical Application Circuit
Functional Pin Description
www.richtek.com
2
(Exposed Pad)
(Exposed Pad)
V
OUT
SOP-8
3.3
2.5
1.8
1.5
1.2
1
1
2
3
4
5
6
7
8
9
(V)
Pin No.
2.7V to 5.5V
PGOOD
(Exposed Pad)
R1 (kΩ)
WDFN-8L 3x3
Chip Enable
V
75
51
30
21
12
IN
6
Table 1. Recommended Components Selection for f
1
2
3
4
5
6
7
8
9
R3
100k
R2 (kΩ)
COMP
SS
EN
VIN
LX
RT
FB
PGOOD
GND
Pin Name
R
10µF
C
24
OSC
24
24
24
24
24
IN
4
8
6
3
VIN
PGOOD
RT
EN
RT8070
Error Amplifier Compensation Point. The current comparator
threshold increases with this control voltage. Connect external
compensation elements to this pin to stabilize the control loop.
Soft-Start Control Input. Connect a capacitor from SS to GND to
set the soft-start period. A 10nF capacitor sets the soft-start
period to 800μs (typ.).
Enable Control Input. Float or connect this pin to logic high for
enable. Connect to GND for disable.
Power Input Supply. Decouple this pin to GND with a capacitor.
Internal Power MOSFET Switches Output. Connect this pin to
the inductor.
Oscillator Resistor Input. Connect a resistor from this pin to
GND sets the switching frequency. If this pin is floating, the
frequency will be set at 2MHz internally.
Feedback Pin. Receives the feedback voltage from a resistive
divider connected across the output.
Power Good Indicator. This pin is an open drain logic output
that is pulled to ground when the output voltage is not within
±12.5% of regulation point.
Ground Pin. The exposed pad must be soldered to a large PCB
and connected to GND for maximum power dissipation.
R
COMP
COMP
GND
8.2
SS
33
22
15
13
11
LX
FB
(kΩ)
5
7
1
9 (Exposed Pad)
2
R
C
0.1nF
COMP
C
SS
COMP
L
560
560
560
560
560
560
(pF)
Pin Function
C
COMP
SW
= 1MHz
R1
R2
L (μH)
1.5
1.5
1.5
1.5
2
2
DS8070-03 March 2011
C
OUT
V
OUT
C
OUT
22
22
22
22
22
22
(μF)