RT4803
2.5MHz, Synchronous Boost Regulator with Bypass Mode
General Description
Features
The RT4803 allows systems to take advantage of new
battery chemistries that can supply significant energy
when the battery voltage is lower than the required
voltage for system power ICs. By combining built-in
power transistors, synchronous rectification, and low
supply current; this IC provides a compact solution for
systems using advanced Li-Ion battery chemistries.
The RT4803 is available in the WL-CSP-16B 1.67x1.67
(BSC) package.
VSEL = L 3.3V
VSEL = H 3.55V
Maximum Continuous Load Current : 2A at VIN >
2.65V Boosting VOUT to 3.35V
Up to 96% Efficient
True Bypass Operation when VIN > Target VOUT
The RT4803 is a boost regulator designed to provide a
minimum output voltage from a single-cell Li-Ion battery,
even when the battery voltage is below system
minimum. In boost mode, output voltage regulation is
guaranteed to a maximum load current of 2A.
Quiescent current in Shutdown Mode is less than 1A,
which maximizes battery life. The regulator transitions
smoothly between Bypass and normal Boost Mode.
The device can be forced into Bypass Mode to reduce
quiescent current.
4 Few External Components : 0.47H Inductor
and 0603 Case Size Input and Output Capacitors
Input Voltage Range : 1.8V to 5V
Output Range from 2.85V to 4.4V
Internal Synchronous Rectifier
Soft-Start with True Load Disconnect
Forced Bypass Mode
VSEL Control to Optimize Target VOUT
Short-Circuit Protection
I2C Controlled Interface
Ultra low Operating Quiescent Current
Small WL-CSP 16B Package
Discharge Function
Applications
Single-Cell Li-Ion, LiFePO4 Smart-Phones or Tablet
2.5G/3G/4G Mini-Module Data Cards
Simplified Application Circuit
RT4803
VOUT
VIN
CIN
+
-
COUT
L1
LX
To pull high voltage
VSEL
EN
nBYP
SDA
SCL
PGOOD
AGND PGND
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT4803
Ordering Information
Pin Configuration
(TOP VIEW)
RT4803
Package Type
WSC : WL-CSP-16B 1.67x1.67 (BSC)
A1
B1
Note :
VSEL
Richtek products are :
C1
RoHS compliant and compatible with the current
Suitable for use in SnPb or Pb-free soldering processes.
A3
B2
D1
A4
VIN
B3
B4
SCL VOUT VOUT
C2
nBYP SDA
requirements of IPC/JEDEC J-STD-020.
A2
EN PGOOD VIN
D2
C3
C4
LX
LX
D3
D4
AGND PGND PGND PGND
WL-CSP-16B 1.67x1.67 (BSC)
Marking Information
0G : Product Code
W : Date Code
0GW
Functional Pin Description
Pin No.
Pin Name
Pin Function
A1
EN
Enable. When this pin is HIGH, the circuit is enabled.
A2
PGOOD
Power good. It is a open-drain output. PGOOD pin pulls low automatically if
the overload or OTP event occurs.
VIN
Input voltage. Connect to Li-Ion battery input power source.
B1
VSEL
Output voltage select. When boost is running, this pin can be used to select
output voltage
B2
SCL
Serial interface clock. (Pull down if I2C is non-used).
B3, B4
VOUT
Output voltage. Place COUT as close as possible to the device.
C1
nBYP
Bypass. This pin can be used to activate Forced Bypass Mode. When this
pin is LOW, the bypass switches are turned on and the IC is otherwise
inactive.
C2
SDA
Serial interface date line. (Pull down if I2C is non-used).
LX
Switching node. Connect to inductor.
D1
AGND
Analog ground. This is the signal ground reference for the IC. All voltage
levels are measured with respect to this pin.
D2, D3, D4
PGND
Power ground. This is the power return for the IC. The COUT bypass
capacitor should be returned with the shortest path possible to these pins.
A3, A4
C3, C4
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Functional Block Diagram
VIN
Current
Sense
VMIN
Control
OSC
+
SCL
SDA
nBYP
VSEL
EN
PGOOD
+
Digital
Soft-Start
Control
+
+
-
-
PWM
Logic
VOUT
Power
MOS
Control
Stage
VMAX
Control
LX
PSM
Control
ZCD
Discharge
AGND
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
PGND
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3
RT4803
Operation
The RT4803 combined built-in power transistors,
Startup and Shutdown State
synchronous rectification, and low supply current, it
provides a compact solution for system using advanced
Li-Ion battery chemistries.
When VIN is rising and through the LIN state, it will
enter the Startup state. If EN is pulled low, any function
is turned-off in shutdown mode.
In boost mode, output voltage regulation is guaranteed
to a maximum load current of 2A. Quiescent current in
Shutdown mode is less than 1A, which maximizes
battery life.
Mode
Soft-Start State
It starts to switch in Soft-start state. After the LIN state,
output voltage is rising with the internal reference
voltage.
There is a point, it will go to fault condition, if the large
output capacitor is used and the timeout is over 2ms
after the soft-start state.
Depiction
Condition
LIN 1
Linear startup 1
VIN > VOUT
LIN 2
Linear startup 2
VIN > VOUT
Soft-Start
Boost soft-start
VOUT < VOUT(MIN)
Fault State
Boost
Boost mode
VOUT = VOUT(MIN)
Bypass
Bypass mode
VIN > VOUT(MIN)
As the Figure 1 shown, it will enter to the Fault state as
below,
LIN
LIN State
When VIN is rising, it enters the LIN State. There are
two parts for the LIN state. It provides maximum current
for 1A to charge the COUT in LIN1, and the other one is
for 2A in LIN2. By the way, the EN is pulled high and
VIN > UVLO.
As the figure shown, if the timeout is over the
specification, it will enter the Fault mode.
EN = 1,
Vin > UVLO
The timeout of LIN2 is over the 1024s.
It is over the 2ms when the state changed from
Soft-start state to Boost mode.
It will be the high impedance between the input and
output when the fault is triggered. A restart will be start
after 1ms.
Boost Mode
There are two normal operation modes, one is the
Boost mode, and the other one is Bypass mode. In the
Boost mode, it provides the power to load by internal
synchronous switches after the soft-start state.
LIN 1
Timeout < 512μs
Bypass Mode
Timeout > 512μs
Soft-Start
Timeout
< 1024μs
Timeout > 2ms
Timeout < 2ms
LIN 2
Timeout > 1024μs
Bypass Mode Operation
Fault
State
Boost
mode
Figure 1. RT4803 State Chart
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
4
In Bypass mode, the differential voltage between VIN
and VOUT is 250mV. Output voltage will increase when
the input voltage is rising after the soft-start state.
In automatic mode, it transits from Boost mode to
Bypass mode. As the Figure 2 shown, there are three
MOSFET (Q1 to Q3). The Q1 & Q2 is for Boost mode, it
is used by Q3 for Bypass mode. VOUT will be followed
the VIN when VIN is higher than the target output
voltage. As the Figure 3 shown, it is transited by bypass
MOSFET (Q3). VOUT followed the VIN.
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
PGOOD (Power Good)
VOUT
Power good is a open-drain input. If it is 0, it stands for
fault occurred. The power good provide the information
to show the state of the system,
Q3
PGOOD pin show high when the sequence of
soft-start is completed.
Any fault cause PGOOD to be pulled low.
PGOOD low when PMIS current limit has triggered
for OR the die the temperature exceeds 120C.
PGOOD is re-asserted when the device cools below
to 100C.
Q1
VIN
LX
Q2
GND
Figure 2. Boost Converter With Bypass Mode
OCP
The converter senses the current signal when the
VOUT
high-side P-MOSFET turns on. As a result, the OCP is
cycle by-cycle current limitation. If the OCP occurs, the
VIN
converter holds off the next on pulse until inductor
current drops below the OCP limit.
OTP
The converter has an over-temperature protection.
When the junction temperature is higher than the
thermal shutdown rising threshold, the system will be
Figure 3. RT4803 mode changed
latched and the output voltage will no longer be
regulated until the junction temperature drops under the
falling threshold.
Force Pass-Through Mode
EN & nBYP
When EN pulled high and nBYP pulled low. The device
is active in the Force pass-through mode. It supplies
current is approximately 15A typ. From the battery,
the device is short circuit protected by a current limit of
4000mA.
VSEL
It is concerned the minimum output voltage at the
heavy load condition. There are two output voltage
levels (3.3V & 3.55V) in Boost mode and Bypass mode.
It can be selected by VSET, so it must not be floating.
It is used to select mode. As the table 1 shown, there
are four device states.
If the EN pull low, and nBYP pull high/low, the RT4803
is forced in shut-down mode and the quiescent is less
than 1A. It works in force pass-through mode, if the
EN set high and nBYP set low. When EN and nBYP
both pull high, the RT4803 is normal operation and
enter automatic mode. There should be a delay time
(> 60S) from EN pull high to nBYP pull high to
guarantee normal automatic mode operation.
Discharge
The RT4803 features the discharge function to release
the output power when the EN pin goes low condition.
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
RT4803
Table 1
EN input
nBYP Input
Device State
0
0/1
1
0
The device is active in forced pass-through mode.
The device supply current is approximately 15A typ. From the battery. The
device is short circuit protected by a current limit of ca. 4000mA.
1
1
The device is active in auto mode (dc/dc boost, pass-through mode)
The device supply current is approximately 65A typ. from the battery
The device is shut down and the shut down current is down to 1A.
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
6
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Absolute Maximum Ratings
(Note 1)
VIN, VOUT to AGND ---------------------------------------------------------------------------------------- 0.2V to 6V
EN, VSEL, PGOOD, nBYP to AGND ------------------------------------------------------------------ 0.2V to 6V
LX ---------------------------------------------------------------------------------------------------------------- (PGND 0.2V) to 6V
Power Dissipation, PD @ TA = 25C
WL-CSP-16B 1.67x1.67 (BSC) --------------------------------------------------------------------------- 2.09W
Package Thermal Resistance
(Note 2)
WL-CSP-16B 1.67x1.67 (BSC), JA --------------------------------------------------------------------- 47.7C/W
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------- 260C
Junction Temperature --------------------------------------------------------------------------------------- 150C
Storage Temperature Range ------------------------------------------------------------------------------ 65C to 150C
ESD Susceptibility
(Note 3)
HBM (Human Body Model) -------------------------------------------------------------------------------- 2kV
MM (Machine Model) ---------------------------------------------------------------------------------------- 200V
CDM (Charge Device Model)------------------------------------------------------------------------------ 1kV
Recommended Operating Conditions
(Note 4)
Input Voltage Range --------------------------------------------------------------------------------------- 1.8V to 5V
Output Voltage Range ------------------------------------------------------------------------------------- 2.85V to 4.4V
Ambient Temperature Range------------------------------------------------------------------------------ 40C to 85C
Junction Temperature Range ----------------------------------------------------------------------------- 40C to 125C
Electrical Characteristics
(VIN = 3V, VOUT = 3.55V, TA = 25C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
1.8
--
5
V
VIN Operation Range
VIN
VIN Quiescent Current
IQ
Auto Bypass Mode, VIN = 3.8V
--
40
70
A
VIN Quiescent Current
IQ
Boost mode, ILOAD = 0mA,
Switching, VIN = 3V
--
65
100
A
VIN Quiescent Current
IQ
Force Bypass , VIN = 3.6V
--
15
25
A
VIN Shutdown Current
ISHDN
EN = 0V, VIN = 3.6V
--
--
1
A
VOUT = 5V, EN = nBYP = H,
VIN < VOUT
--
0.2
1
A
VOUT to VIN Reverse Leakage ILK
VOUT Discharge Impedance
R_DIS_OUT EN = L
--
80
--
Under Voltage Lock Out
VUVLO
--
1.6
1.8
V
Under Voltage Lock Out
Hysteresis
VUVLO_HYS
--
200
--
mV
PGOOD Low
PGOOD Leakage Current
Logic Level High EN, VSEL,
nBYP, SCL, SDA
VIN Rising
VPGOOD
IPGOOD = 5mA
--
--
0.4
V
IPGOOD _LK
VPGOOD = 5V
--
--
1
A
1.2
--
--
V
VIH
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
7
RT4803
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
--
--
0.4
V
Logic Level Low EN, VSEL,
nBYP, SCL, SDA
VIL
Output Voltage Accuracy
VREG
VOUT VIN > 100mV, PWM
2
--
2
%
Minimum On Time
TON
VIN = 3V, VOUT = 3.5V,
ILOAD > 1000mA
--
80
--
ns
Maximum Duty Cycle
DMAX
40
--
--
%
Switching Frequency
FSW
VIN = 2.65V, VOUT = 3.5V,
ILOAD = 1000mA
2
2.5
3
MHz
Boost Valley Current Limit
ICL
VIN = 2.9V
4.4
5
5.6
A
Soft-Start Input Current Limit
ISS_PK
LIN1
--
1000
--
mA
Soft-Start Input Current Limit
ISS_PK
LIN2
--
2000
--
mA
Pass Through Mode Current
Limit
IBPCL
VIN = 3.2V
--
4
--
A
N-channel Boost Switch
RDS(ON)
RDSN
VIN = 3.2V, VOUT = 3.5V
--
60
95
m
P-channel Boost Switch
RDS(ON)
RDSP
VIN = 3.2V, VOUT = 3.5V
--
40
80
m
N-channel Bypass Switch
RDS(ON)
RDSP_BYP
VIN = 3.2V, VOUT = 3.5V
--
40
60
m
Hot Die Trigger Threshold
THD
--
100
--
o
--
o
Hot Die Release Threshold
THDR
--
90
C
C
Over Temperature Protection
TOTP
--
160
--
o
Over Temperature Protection
Hysteresis
TOTP_HYS
--
20
--
o
FAULT Restart Time
TRST
--
1
--
ms
C
C
Note 1. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These
are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect
device reliability.
Note 2. JA is measured at TA = 25C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
8
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Typical Application Circuit
RT4803
A3
+
-
CIN
10μF
L1
0.47μH
To pull high voltage
1k
1k
VOUT
VIN
B3, B4
COUT
22μF x 2
C3, C4
LX
B1 VSEL
A1
EN
C1
nBYP
C2
SDA
B2 SCL
To pull high voltage
1M
PGOOD
A2
AGND PGND
D1
D2, D3, D4
BOM of Test Board
Reference
Description
Manufacturer
Package
Parameter
Typ.
Unit
CIN
10F/16V/X5R
Taiyo : EMK212ABJ106KG
0805
C
10
F
COUT
22F/10V/X5R
Taiyo : LMK212BBJ226MG
0805
C
22
F
L1
0.47μH, 20%
TOKO : DFE2520F-R47M
2520
L
0.47
H
DCR (Series R)
29
m
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
9
RT4803
Typical Operating Characteristics
Efficiency vs. Load Current
Efficiency vs. Load Current
100
95
95
90
VIN = 2.5V
VIN = 2.7V
85
VIN = 3V
VIN = 3.3V
80
VIN = 2.5V
90
Efficiency (%)
Efficiency (%)
100
VIN = 2.7V
VIN = 3V
85
VIN = 3.3V
80
75
75
VOUT = 3.55V, ILOAD = 1mA to 2A
VOUT = 3.55V, ILOAD = 100mA to 2A
70
70
0.001
0.01
0.1
1
0.1
10
1
Efficiency vs. Load Current
100
95
95
VIN = 2.5V
Efficiency (%)
Efficiency (%)
Efficiency vs. Load Current
100
90
VIN = 2.7V
VIN = 3V
85
10
Load Current (A)
Load Current (A)
80
VIN = 2.5V
90
VIN = 2.7V
VIN = 3V
85
80
75
75
VOUT = 3.3V, ILOAD = 100mA to 2A
VOUT = 3.3V, ILOAD = 1mA to 2A
70
70
0.001
0.01
0.1
1
0.1
10
1
10
Load Current (A)
Load Current (A)
Output Regulation vs. Load Current
Output Regulation vs. Load Current
0.03
0.03
VIN = 2.8V
Output Regulation (%)
Output Regulation (%)
VIN = 2.5V
0.02
VIN = 3V
VIN = 3.3V
0.01
0
-0.01
VIN = 2.5V
0.02
VIN = 2.8V
VIN = 3V
0.01
0
-0.01
VOUT = 3.3V, ILOAD = 0A to 2A
VOUT = 3.55V, ILOAD = 0A to 2A
-0.02
-0.02
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Load Current (A)
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
10
2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Load Current (A)
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Output Ripple vs. Load Current
Output Ripple vs. Load Current
70
70
VOUT = 3.55V, ILOAD = 0A to 2A
VOUT = 3.3V, ILOAD = 0A to 2A
60
Output Rippie (mV)
Output Rippie (mV)
60
VIN = 2.5V
50
VIN = 2.7V
40
VIN = 3V
VIN = 3.3V
30
20
50
40
VIN = 2.5V
VIN = 2.7V
30
VIN = 3V
VIN = 3.2V
20
10
10
0
0
0
500
1000
1500
0
2000
500
1000
1500
2000
Load Current (mA)
Load Current (mA)
Maximum Load Current vs. Input Voltage
Startup
Maximum Load Current (A)1
5.0
4.0
3.0
VOUT
(2V/Div)
2.0
ILX
(1A/Div)
1.0
EN
(5V/Div)
PGOOD
(5V/Div)
VIN = 2.5V to 3.7V, V OUT = 3.55V
0.0
2.5
2.7
2.9
3.1
3.3
3.5
3.7
Time (100s/Div)
Input Voltage (V)
Startup
VIN = 3V, VOUT = 3.3V, Load = 50
VIN = 3V, VOUT = 3.55V, Load = 50
Overload Protection
VOUT
(2V/Div)
VIN = 3V, VOUT = 3.55V
VOUT
(2V/Div)
ILX
(1A/Div)
ILX
(2A/Div)
EN
(5V/Div)
PGOOD
(5V/Div)
PGOOD
(5V/Div)
Time (100s/Div)
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
Time (1ms/Div)
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
RT4803
Overload Protection
VOUT
(200mV/Div)
VOUT
(2V/Div)
ILX
(2A/Div)
PGOOD
(5V/Div)
Load Transient
IOUT
(200mA/Div)
VIN = 3V, VOUT = 3.55V,
ILOAD = 100mA to 500mA
VIN = 3V, VOUT = 3.3V
Time (1ms/Div)
Time (25s/Div)
Load Transient
Transient Overload
VOUT
(200mV/Div)
VOUT
(500mV/Div)
VIN = 3V, VOUT = 3.55V,
ILOAD = 1A to 3.8A
IOUT
(200mA/Div)
IOUT
(2A/Div)
VIN = 3V, VOUT = 3.3V,
ILOAD = 100mA to 500mA
Time (25s/Div)
PGOOD
(5V/Div)
Time (50s/Div)
Transient Overload
VOUT
(500mV/Div)
VIN = 3V, VOUT = 3.3V,
ILOAD = 1A to 3.8A
IOUT
(2A/Div)
PGOOD
(5V/Div)
Time (50s/Div)
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
12
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Application Information
restarts if the input voltage recovers to the input
Enable
voltage UVLO high level.
The device can be enabled or disabled by the EN pin.
When the EN pin is higher than the threshold of
logic-high, the device starts operating with soft-start.
Once the EN pin is set at low, the device will be shut
down. In shutdown mode, the converter stops
switching, internal control circuitry is turned off, and
the load is disconnected from the input. This also
means that the output voltage can drop below the
input voltage during shutdown.
Thermal Shutdown
The device has a built-in temperature sensor which
monitors the internal junction temperature. If the
temperature exceeds the threshold, the device stops
operating. As soon as the IC temperature has
decreased below the threshold with a hysteresis, it
starts operating again. The built-in hysteresis is
designed to avoid unstable operation at IC
temperatures near the over temperature threshold.
Soft-Start State
After the successful completion of the LIN state (VOUT
≥ VIN300mV).
During Soft-Start state, VOUT is ramped up by Boost
internal loop. If VOUT fails to reach target value during
the Soft-Start period for more than 2ms, a fault
condition is declared.
Inductor Selection
The recommended nominal inductance value is
0.47H.
It is recommended to use inductor with dc saturation
current ≥ 3500mA
Input Capacitor Selection
Output Voltage Setting
User can select the output voltage level by VSEL and
I2C. If the VSEL pulled low, the default is 3.3V, and if
it pulled high, the default is 3.55V.
The output voltage range is from 2.85V to 4.4V.
At least a 10F input capacitor is recommended to
improve transient behavior of the regulator and EMI
behavior of the total power supply circuit for LX. And
at least a 1F ceramic capacitor placed as close as
possible to the VIN and GND pins of the IC is
recommended.
Power Save Mode
PSM is the way to improve efficiency at light load.
When the output voltage is lower than a set threshold
voltage, the converter will operate in PSM.
Output Capacitor Selection
At least 22F x 2 capacitors is recommended to
improve VOUT ripple.
It raises the output voltage with several pulses until
the loop exits PSM.
Output voltage ripple is inversely proportional to
COUT.
Under-Voltage Lockout
Output capacitor is selected according to output ripple
which is calculated as :
The under-voltage lockout circuit prevents the device
from operating incorrectly at low input voltages. It
prevents the converter from turning on the power
switches under undefined conditions and prevents the
battery from deep discharge. VIN voltage must be
greater than 1.7V to enable the converter. During
operation, if VIN voltage drops below 1.6V, the
converter is disabled until the supply exceeds the
UVLO rising threshold. The RT4803 automatically
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
VRIPPLE(P P) tON
and
ILOAD
COUT
V
tON tSW D tSW 1 IN
V
OUT
therefore :
V
ILOAD
COUT tSW 1 IN
VOUT VRIPPLE(P P)
and
1
tSW
fSW
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
13
RT4803
The maximum VRIPPLE occurs when VIN is at
minimum and ILOAD is at maximum.
Output Discharge Function
With the EN pin set to low, the VOUT pin is internally
connected to GND by an internal discharge
N-MOSFET switch.
This feature prevents residual charge voltages on
capacitor connected to VOUT pins, which may impact
proper power up of the system.
Current Limit
The RT4803 employs a valley-current limit detection
scheme to sense inductor current during the off-time.
When the loading current is increased such that the
loading is above the valley current limit threshold, the
off-time is increased until the current is decreased to
valley-current threshold. Next on-time begins after
current is decreased to valley-current threshold.
On-time is decided by (VOUT VIN) / VOUT ratio. The
output voltage decreases when further loading
current increase. As the following figure shown, the
current limit function is implemented by the scheme.
IIN (DC)
Valley Current Limit
f
Inductor Current
DIL
DIL =
IIN (DC)
VIN D
L
f
Figure 4. Inductor Currents In Current Limit Operation
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
14
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Register Table Lists [Slave address = 1110101 (0x75)]
Name
Address
Description
CONFIG
0x01
MODE control & Spread modulation control
VOUTFLOOR
0x02
Output Voltage Selection
VOUTROOF
0x03
Output Voltage Selection
ILIMSET
0x04
Set current limit & Softstart current limit
STATUS
0x05
Read IC status
I2C Interface
The RT4803 I2C slave address is 1110101 (7bits). The I2C interface supports fast mode (bit rate up to 400kb/s).
The write or read bit stream (N 1) is shown below :
Read N bytes
S
Slave Address
0 A
Register Address
A Sr
Assume Address = m
R/W
MSB
Data 2
Slave Address
1 A MSB
Data 1
LSB A
Data for Address = m
LSB A
Data for Address = m+1
MSB
Data N
LSB A P
Data for Address = m + N - 1
Write N bytes
S
Slave Address
0 A
R/W
Register Address
Assume Address = m
A MSB
Data 1
Data for Address = m
MSB
LSB A MSB
Data 2
Data for Address = m + 1
Data N
LSB A
LSB A P
Data for Address = m + N - 1
Driven by Master,
Driven by Slave (RT4803),
P Stop,
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
S Start,
Sr Repeat Start
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
15
RT4803
Offset 0x01
CONFIG
Bits
7
6
5
Name
RESET
Reset
0
0
Type
RW
RW
4
3
2
RESERVED
PG Config
SSFM
0
0
1
0
0
1
RW
RW
RW
RW
RW
RW
2
1
0
ENABLE[1:0]
Offset 0x02
Bits
7
1
0
MODE_CTRL[1 : 0]
VOUTFLOOR
6
5
4
3
Name RESERVED RESERVED RESERVED
VOUT[4: 0]
Reset
0
0
0
0
1
0
0
1
Type
RW
RW
RW
RW
RW
RW
RW
RW
2
1
0
Offset 0x03
Bits
7
VOUTROOF
6
5
4
3
Name RESERVED RESERVED RESERVED
VOUT[4: 0]
Reset
0
0
0
0
1
1
1
0
Type
RW
RW
RW
RW
RW
RW
RW
RW
2
1
0
Offset 0x04
Bits
7
ILIMSET
6
Name RESERVED RESERVED
5
4
ILIM_OFF
SOFT_START
3
ILIM[3:0]
Reset
0
0
0
1
1
1
1
1
Type
RW
RW
RW
RW
RW
RW
RW
RW
Offset 0x05
STATUS
Bits
7
6
5
4
3
2
1
0
Name
TSD
HOTDIE
DCDCMODE
OPMODE
ILIMPT
ILIMBST
FAULT
PGOOD
Reset
0
0
0
0
0
0
0
0
Type
RO
RO
RO
RO
RO
RO
RO
RO
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
16
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Name
Function
Addr
CONFIG
MODE control &
Spread modulation
control
0x01
Name
Reset
Bit
Mode
7
R/W
RESET
Description
0
0 : Disable ID detection function
1 : Enable ID detection function
00 : Device operation follows hardware control signal
(refer to table 1)
01 : Device operation in auto transition mode (boost/bypass)
regardless of the nBYP control signal (EN = 1)
10 : Device is forced in pass-through mode regardless of the nBYP
control signal (EN = 1)
11 : Device is in shutdown mode. The output voltage is reduced to a
minimum value (VIN VOUT 3.6V) regardless of the nBYP
control signal (EN = 1)
[6 : 5]
R/W
ENABLE[1 : 0]
0
4
R/W
Reserved
0
3
R/W
PG Config
1
0 : PG pin = H, Power good indication
PG pin = L, IC shut down, it needs retoggle this pin to restart
VOUT
1 : PG pin is for power good indication
2
R/W
SSFM
0
0 : Spread spectrum modulation is disabled.
1 : Spread spectrum modulation is enabled in PWM mode.
MODE_CTRL[1 : 0]
01
00 : Device operation follows hardware control signal.
01 : PFM with automatic transition into PWM operation.
10 : Forced PWM operation.
11 : PFM with automatic transition into PWM operation (VSEL = L),
forced PWM operation (VSEL = H).
Name
Function
Addr
VOUTFLOOR
Output Voltage
Selection
0x02
Name
Reset
[1 : 0]
R/W
Bit
Mode
[7 : 5]
R/W
[4 : 0]
R/W
Reserved
VOUT[4 : 0]
000
00000 : VOUT = 2.85V
00001 : VOUT = 2.9V
00010 : VOUT = 2.95V
00011 : VOUT = 3V
01001 00100 : VOUT = 3.05V
…
01001 : VOUT = 3.3V (default)
…
11111 : VOUT = 4.4V
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
Description
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
17
RT4803
Name
Function
Addr
VOUTROOF
Output Voltage
Selection
0x03
Name
Reset
Bit
Mode
[7 : 5]
R/W
[4 : 0]
R/W
Reserved
VOUT[4 : 0]
Description
000
00000 : VOUT = 2.85V
00001 : VOUT = 2.9V
00010 : VOUT = 2.95V
00011 : VOUT = 3V
01110 00100 : VOUT = 3.05V
…
01110 : VOUT = 3.55V (default)
…
11111 : VOUT = 4.4V
Name
Function
Addr
ILIMSET
Set current limit &
Soft-start current
limit
0x04
Name
Reset
Bit
Mode
[7 : 6]
R/W
Reserved
00
5
R/W
ILIM_OFF
0
0 : Current Limit Enabled
1 : Current Limit Disabled
4
R/W
Soft-Start
1
0 : Boost soft-start current is limited per ILIM bit settings
1 : Boost soft-start current is limited to ca. 1250mA inductor valley
current
[3 : 0]
R/W
ILIM[3 : 0]
1111
Description
1000 : 1500mA
1001 : 2000mA
1010 : 2500mA
1011 : 3000mA
1100 : 3500mA
1101 : 4000mA
1110 : 4500mA
1111 : 5000mA (default)
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
18
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
Name
Function
Addr
STATUS
Read IC status
0x05
Name
Reset
Bit
Mode
Description
7
R
TSD
0
0 : Normal operation.
1 : Thermal shutdown tripped. The flag is reset after readout.
6
R
HOTDIE
0
0 : TJ < 115°C.
1 : TJ > 115°C.
5
R
DCDCMODE
0
0 : Device operates in PFM mode.
1 : Device operates in PWM mode.
4
R
OPMODE
0
0 : Device operates in pass-through mode.
1 : Device operates in dc/dc mode.
3
R
ILIMPT
0
0 : Normal operation.
1 : Indicates that the bypass FET current limit has triggered. This
flag is reset after readout.
2
R
ILIMBST
0
0 : Normal operation.
1 : Indicates that the average input current limit has triggered for
1.5ms in dc/dc boost mode. This flag is reset after readout.
1
R
FAULT
0
0 : Normal operation.
1 : Indicates that a fault condition has occurred. This flag is reset
after readout.
0
R
PGOOD
0
0 : Indicates the output voltage is out of regulation.
1 : Indicates the output voltage is within its nominal range. This bit is
set if the converter is forced in pass-through mode.
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
19
RT4803
Thermal Considerations
Layout Consideration
For continuous operation, do not exceed absolute
The PCB layout is an important step to maintain the
high performance of the RT4803.
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature.
The maximum power dissipation can be calculated by
the following formula :
PD(MAX) = (TJ(MAX) TA) / JA
where TJ(MAX) is the maximum junction temperature,
TA is the ambient temperature, and JA is the junction to
ambient thermal resistance.
For recommended operating condition specifications,
the maximum junction temperature is 125C. The
junction to ambient thermal resistance, JA, is layout
dependent. For WL-CSP-16B 1.67x1.67 (BSC)
package, the thermal resistance, JA, is 47.7C/W on a
standard JEDEC 51-7 four-layer thermal test board.
Both the high current and the fast switching nodes
demand full attention to the PCB layout to save the
robustness of the RT4803 through the PCB layout.
Improper layout might show the symptoms of poor line
or load regulation, ground and output voltage shifts,
stability issues, unsatisfying EMI behavior or worsened
efficiency. For the best performance of the RT4803, the
following PCB layout guidelines must be strictly
followed.
Place the input and output capacitors as close as
possible to the input and output pins respectively for
good filtering.
For thermal consider, it needed to maximize the pure
area for the power stage area besides the LX.
The maximum power dissipation at TA = 25C can be
calculated by the following formula :
PD(MAX) = (125C 25C) / (47.7C/W) = 2.09W for
WL-CSP-16B 1.67x1.67 (BSC) package
The maximum power dissipation depends on the
operating ambient temperature for fixed TJ(MAX) and
thermal resistance, JA. The derating curve in Figure 5
allows the designer to see the effect of rising ambient
temperature on the maximum power dissipation.
Maximum Power Dissipation (W)1
2.5
Four-Layer PCB
2.0
1.5
1.0
0.5
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 5. Derating Curve of Maximum Power
Dissipation
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
20
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
RT4803
LX
L
A3
A4
B1
B2
B3
B4
C1
C2
C3
C4
D1
D2
D3
D4
COUT
A2
COUT
CIN
A1
COUT
VOUT
VIN
GND
Figure 6. PCB Layout Guide
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
DS4803-03
January 2020
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
21
RT4803
Outline Dimension
Dimensions In Millimeters
Symbol
Dimensions In Inches
Min
Max
Min
Max
A
0.500
0.600
0.020
0.024
A1
0.170
0.230
0.007
0.009
b
0.240
0.300
0.009
0.012
D
1.620
1.720
0.064
0.068
D1
E
1.200
1.620
0.047
1.720
0.064
0.068
E1
1.200
0.047
e
0.400
0.016
WL-CSP-16B 1.67x1.67 (BSC)
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume
responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and
reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may
result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
Copyright © 2020 Richtek Technology Corporation. All rights reserved.
www.richtek.com
22
is a registered trademark of Richtek Technology Corporation.
DS4803-03
January 2020
工商网监
湘ICP备2023018690号
