RT4722C
Triple DC-DC Boost Converter for AMOLED
General Description
The RT4722C is a triple channels DC-DC converter
which is designed to provide the power of AMOLED. It
integrates step up DC-DC and an inverting converter to
provide the positive and negative output voltage
required by AMOLED.
For the portable application, board space and
efficiency are always major concerns. The high
switching frequency of the RT4722C allows the use of
low inductance inductor to save the board space. For
the negative and AVDD output voltage, both can be
programmed by external MCU through single wire
(SWIRE pin). The output voltage range of negative
output voltage is
1.4V
to
5.4V
and AVDD voltage is
5.8V to 7.9V. RT4722C has OTP, SCP, UVLO and
over-current protections. The RT4722C is available in a
WQFN-16L 3x3 package to achieve saving PCB space.
Features
Boost Converter to Supply Positive AVDD
Voltage from 5.8V to 7.9V
Boost Converter to Supply AMOLED Positive
Voltage 4.6V
Inverter Converter to Supply AMOLED Negative
Voltage from
1.4V
to
5.4V
Maximum Output Current up to 300mA for
AMOLED Positive & Negative Power Supply
Maximum Output Current up to 55mA for AVDD
Output Voltage
Typical Peak Efficiency : 90% (40mA to 150mA)
PWM Mode @ 1.5MHz Switching Frequency
High Output Voltage Accuracy
Excellent Line and Load Transient
Excellent Line and Load Regulation
Programmable Negative and AVDD Voltage by
SWIRE Pin
Fast Outputs Discharge Function
Low Quiescent Current < 1A in Shutdown Mode
Internal Soft-Start to limit Inrush Current
Over-Temperature Protection (OTP)
Over-Current Protection (OCP)
Short Circuit Protection (SCP)
Applications
AMOLED Panel
PDAs and Smart Phones
Probable Instrument
Simplified Application Circuit
VBAT
L1
CIN
LX1
V
POS
CVO1
V
POS_FB
AVDD Enable
VO1, VO2 Enable and Program VO2
VO1
RT4722C
LX2
VO2
CVO2
V
NEG
PVIN
LX3
VO3
AVIN
CAV
L2
AVDD
CVO3
L3
FBS
ENO3
FD
SWIRE
PGND1 PGND2 AGND
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4722C-00
September 2017
www.richtek.com
1
RT4722C
Ordering Information
RT4722C
Package Type
QW : WQFN-16L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
Pin Configuration
(TOP VIEW)
AVIN
LX3
PGND2
VO3
16 15 14 13
LX1
PGND1
VO1
FBS
1
2
3
4
5
6
7
8
12
AGND
17
11
10
9
PVIN
LX2
VO2
SWIRE
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
LK=YM
DNN
LK= : Product Code
YMDNN : Date Code
WQFN-16L 3x3
Functional Pin Description
Pin No.
1
2
3
4
5
6
Pin Name
LX1
PGND1
VO1
FBS
FD
NC
Pin Function
1
st
boost converter switching node.
Power ground.
1
st
boost converter output.
1
st
boost converter output feedback sense. Connect to VO1 pin if un-used.
Active discharge enable/disable during shutdown. Default floating.
No connected.
Signal ground. The exposed pad must be soldered to a large PCB and
connected to AGND for maximum power dissipation.
2
nd
boost enable/disable pin.
V
POS
, V
NEG
control pin (enable/disable pin).
Buck/Boost converter output (negative voltage).
Buck/Boost converter switching node.
Power input voltage.
2
nd
boost converter output.
Power ground.
2
nd
boost converter switching node.
Analog input voltage.
7,
AGND
17 (Exposed Pad)
8
9
10
11
12
13
14
15
16
ENO3
SWIRE
VO2
LX2
PVIN
VO3
PGND2
LX3
AVIN
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
FD
NC
AGND
ENO3
DS4722C-00
September 2017
RT4722C
Functional Block Diagram
AVIN
UVLO
PVIN
PVIN
Switching
Well
LX3
VO3
ZCD3
SCP3
ENO3
VO3
P3
Pulse
Diming
PWM
Logic
OCP3
Soft-start
VRX3
GM
FB3
RP6
FB3
RP5
N3
LX1
VO1
VR1
1.5MHz
OSC
PVIN1
Switching
Well
VO1
FBS
R1A
VRX’
P1
RP2
FB1
GM
R1B
PWM
Logic
VRX
GM
N1
SCP1
RP1
OCP1
Soft-start
Swire
FB1
Pulse Dimming
PVIN
VRX’
NN1
RDIMP
FB2
RDIMN
GM
OCP2
PWM
Logic
LX2
SCP2
Soft-
start
NN2
VO2
VO2
VO1
Fast Discharge
VO2
VO3
OTP
FD
AGND
PGND1
PGND2
Operation
The RT4722C is a triple channels DC-DC converter
which is designed to provide the power of AMOLED
that can support the input voltage range from 2.9V to
4.5V. The VO1 & VO2 output current can be up to
300mA, and the VO3 output current can be up to 55mA.
The RT4722C uses current mode architecture for the
purpose of high efficiency and high transient response.
The VO1 positive output voltage is produced from the
DC-DC Boost converter and is set at a typical value of
4.6V. When the SWIRE goes high, the positive output
voltage will be enabled with an internal soft-start
process. The VO2 negative output voltage is produced
from the DC-DC Buck-Boost converter and the
negative output voltage range is
1.4V
to
5.4V.
It can
be programmed by external MCU through single wire
(SWIRE pin). The VO3 positive output voltage is
produced from the DC-DC Boost converter and is set
from 5.8V to 7.9V by SWIRE pin. When SWIRE goes
high and VO1 soft-start had finished already, negative
output voltage VO2 will be enabled with an internal
soft-start process.
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4722C-00
September 2017
www.richtek.com
3
RT4722C
Table 1. SWIRE Command LUT for VO2
Bit (Pulse)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
VNEG (V)
4
(Default)
5.4
5.3
5.2
5.1
5
4.9
4.8
4.7
4.6
4.5
4.4
4.3
4.2
4.1
4
3.9
3.8
3.7
3.6
3.5
Bit (Pulse)
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
VNEG (V)
3.4
3.3
3.2
3.1
3
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2
1.9
1.8
1.7
1.6
1.5
1.4
Bit (Pulse)
0
42
43
44
45
46
47
48
49
AVDD (V)
6.1 (Default)
7.9
7.6
7.3
7
6.7
6.4
6.1
5.8
Table 2. SWIRE Pin Characteristics
Rating
Initial Waiting Time
Signal Stop Indicate Time
Turn-off Detection Time
SWIRE Rising Time
SWIRE Falling Time
Clock SWIRE High
Clock SWIRE Low
Input SWIRE Frequency
Symbol
t
wait_int
t
stop
t
off_dly
t
r
t
f
t
sH
t
sL
f
swire
Min
--
100
30
--
--
2
2
25
Typ
50
--
--
--
--
10
10
--
Max
--
--
80
200
200
20
20
250
Unit
s
s
s
ns
ns
s
s
kHz
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS4722C-00
September 2017
RT4722C
Table 3. Fast Discharge Selection
SWIRE (Pulse)
0
FD Pin
High
Low
High
Low
High
Low
Discharge
ON
OFF
ON
ON
OFF
OFF
Note
FD Control
50
SWIRE Control
51
SWIRE Control
Table 4. Control of Transient Time
CTRL (Pulse)
0
52
53
Step Voltage per 100mV (mV)
0
50
25
Note
No Division Change
2 Division Change
4 Division Change
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4722C-00
September 2017
www.richtek.com
5
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