®
RT9278
High Efficiency Boost LDO Converter & High Power White
LED Driver
General Description
The RT9278 is a compact, high
efficiency,
synchronous
step-up converter, it provides a power supply solution for
products powered by either two-cell, three-cell Alkaline/
NiMH or one-cell Li-Ion/Li-polymer battery.
The RT9278 is boost converter with PWM control loop,
provide up to 95% efficiency by using a synchronous
rectifier. The maximum peak current in the internal switch
is limited to up to 2A.
It keeps the output voltage regulated when the input
voltage exceeds the setting output voltage. The output
voltage can be set by an external resister divider, or be
fixed to reduce external components. It integrates a linear
controller for linear regulator.
RT9278 is available in VDFN-10L 3x3 package.
Features
95% Efficiency Synchronous Boost Converter
High Supply Capability
2A Current Limit
Input Voltage Range : 1.5V to 5.5V
600kHz Fixed Switching Rate
Adjustable Output Voltage Options Up to 5.5V
Output Voltage Keep Regulated when Input Voltage
Exceed Setting Output Voltage
1uA Supply Current in Shutdown Mode
External Compensation Network
Build in Linear Controller for Linear Regulator
Over Temperature Protection
Small 10-Lead VDFN Package
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Ordering Information
RT9278
Package Type
QV : VDFN-10L 3x3 (V-Type)
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
RT9278QQV
Digital Still Camera
Camera White LED Flash Light
PDAs
Portable Device
Marking Information
RT9278PQV
AC- : Product Code
AC-YM
DNN
YMDNN : Date Code
Pin Configurations
(TOP VIEW)
FB
COMP
GND
EN
LX
1
2
3
4
5
11
10
9
AC= : Product Code
AC=YM
DNN
LFB
LDRI
PGND
VDD
VOUT
YMDNN : Date Code
GND
8
7
9
VDFN-10L 3x3
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9278-07 January 2012
www.richtek.com
1
RT9278
Typical Application Circuit
Chip Enable
L1
1 to 10µH
V
IN
C1
4.7µF
R1 2.2k
C2
12nF
Chip
Shutdown 100ms
4 EN
5 LX
8
VDD 7
RT9278
VOUT 6
FB 1
LDRI 9
LFB 10
C4
2.2µF
C3
1µF
Q1
AO7401
R2
300k
700mA
100ms
D1
Power LED
PGND
2 COMP
3 GND
R3
0.28
Figure 1. Novel Up-Down Driver for Power LED with Strobe Mode
Note : Patent Pending.
V
IN
Chip Enable
4 EN
VDD 7
L1
RT9278
1 to 10µH Chip Shutdown 5
LX
VOUT 6
8
C1
PGND
4.7µF
FB 1
R1 2.2k 2
COMP LDRI 9
3 GND
LFB 10
C2
12nF
C3
1µF
I
strobe
Q1
AO3403
C4
2.2µF
R2
300k
I
Movie
GPIO
700mA
200mA
2.8V
100ms
0V
D1
Power LED
R4 1k
R5
18.2k
GPIO
R3
0.28
R4
=
1kΩ
R3
=
0.2
I
Strobe
(GPIO_HI
−
0.2) x R4
R5
=
0.2
−
(I
Movie
x R3)
Figure 2. Novel Up-Down Driver for Power LED with Strobe Mode and Movie Mode
Note :
Patent Pending.
The GPIO Signal has to pull high before enable IC.
Chip Enable
L1
4.7uH
V
IN
C1
10µF
VDD 7
EN
Chip Shutdown
RT9278
5 LX
6
R1 2.5k
2 COMP VOUT
8
PGND
9
10 LFB
LDRI
C2
3 GND
FB 1
2.2nF
4
C3
1µF
C4
10µF
Q1
AO3403
R2
510k
C5
100pF
R3
470k
V
OUT
3.3V
R4
150k
Figure 3. Synchronous Boost Converter with Load Disconnect in Shutdown
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS9278-07 January 2012
RT9278
Table 1. Component Selection for Figure 6 (L=2.2µH)
Input Voltage Output Voltage
(V)
(V)
1.5~3.0
1.5~3.3
3.0~4.5
3.3
5.0
5.0
L
(µH)
2.2
2.2
2.2
C
OUT
(µF)
40
40
40
R1
(kΩ)
150
130
130
R2
(kΩ)
470
680
680
R
COMP
(kΩ)
43
24
24
C
COMP
(nF)
5.6
8.2
3.9
C
FF
(pF)
18
12
12
Table 2. Component Selection for Figure 6 (L=4.7µH)
Input Voltage Output Voltage
(V)
(V)
1.5~3.0
1.5~3.3
3.0~4.5
3.3
5.0
5.0
L
(µH)
4.7
4.7
4.7
C
OUT
(µF)
40
40
40
R1
(kΩ)
150
130
130
R2
(kΩ)
470
680
680
R
COMP
(kΩ)
24
24
24
C
COMP
(nF)
10
15
8.2
C
FF
(pF)
18
12
12
Table 3. Component Selection for Figure 6 (L=6.8µH)
Input Voltage Output Voltage
(V)
(V)
1.5~3.0
1.5~3.3
3.0~4.5
3.3
5.0
5.0
L
(µH)
6.8
6.8
6.8
C
OUT
(µF)
40
40
40
R1
(kΩ)
150
130
130
R2
(kΩ)
470
680
680
R
COMP
(kΩ)
24
24
24
C
COMP
(nF)
15
22
12
C
FF
(pF)
18
12
12
Table 4. Component Selection for Figure 6 (L=10µH)
Input Voltage Output Voltage
(V)
(V)
1.5~3.0
1.5~3.3
3.0~4.5
3.3
5.0
5.0
L
(µH)
10
10
10
C
OUT
(µF)
40
40
40
R1
(kΩ)
150
130
130
R2
(kΩ)
470
680
680
R
COMP
(kΩ)
24
24
24
C
COMP
(nF)
22
33
18
C
FF
(pF)
18
12
12
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS9278-07
January 2012
RT9278
Functional Pin Description
Pin No.
1
2
3
4
5
6
7
8
9
10
Pin Name
FB
COMP
GND
EN
LX
VOUT
VDD
PGND
LDRI
LFB
Feedback Input Pin.
Feedback Compensation Pin.
Ground.
Enable Input Pin
Switch Node.
Output Pin
Device Input Power Pin.
Power Ground.
Linear Controller Driver Output.
Linear Controller Feedback Input.
The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Pin Function
11 (Exposed Pad) GND
Function Block Diagram
COMP
Error
AMPLIFIER
-
V
REF
= 0.8V
VDD
GND
Oscillator
and
Shutdown
Control
Slope
Compen-
sation
Current
Sense
+
Error
Comparator
-
+
VOUT
FB
Control
and
Driver
Logic
LX
EN
PGND
LDRI
LFB
V
REF
= 0.2V
-
+
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS9278-07 January 2012
www.richtek.com
5
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