RT4803A

RT4803A
2.5MHz, Synchronous Boost Regulator with Bypass Mode
General Description
Features
The RT4803A 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 RT4803A 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 1A,
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.
The RT4803A is available in the WL-CSP-16B
1.67x1.67 (BSC) package.


4 Few External Components: 0.47H Inductor
and 0603 Case Size Input and Output Capacitors
Input Voltage Range: 1.8V to 5V
Output Range from 2.85V to 4.4V
VSEL = L 3.15V
 VSEL = H 3.4V
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













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
RT4803A
VOUT
VIN
CIN
+
-
COUT
L1
LX
To pull high voltage
VSEL
EN
nBYP
SDA
SCL
GPIO
AGND PGND
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT4803A
Ordering Information
Pin Configurations
(TOP VIEW)
RT4803A
Package Type
WSC : WL-CSP-16B 1.67x1.67 (BSC)
A2
A3
A4
GPIO
VIN
VIN
B2
B3
B4
B1
Note :
VSEL
Richtek products are :

A1
EN
C1
C2
nBYP SDA
RoHS compliant and compatible with the current
D1
requirements of IPC/JEDEC J-STD-020.

SCL VOUT VOUT
D2
C3
C4
LX
LX
D3
D4
AGND PGND PGND PGND
Suitable for use in SnPb or Pb-free soldering processes.
WL-CSP-16B 1.67x1.67 (BSC)
Marking Information
38 : Product Code
W : Date Code
38W
Functional Pin Description
Pin No.
Pin Name
Pin Function
A1
EN
Enable. When this pin is HIGH, the circuit is enabled.
A2
GPIO
General Purpose Input/Output.
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 © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
Function Block Diagram
VIN
Current
Sense
VMIN
Control
OSC
+
SCL
SDA
nBYP
VSEL
EN
GPIO
+
Digital
Soft-Start
Control
+
+
-
-
PWM
Logic
VOUT
Power
MOS
Control
Stage
VMAX
Control
LX
PSM
Control
ZCD
Discharge
AGND
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
PGND
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3
RT4803A
Operation
RT4803A
combined
built-in
power
transistors,
synchronous rectification, and low supply current, it
provides a compact solution for system using advanced
Li-Ion battery chemistries.
In boost mode, output voltage regulation is guaranteed
to a maximum load current of 2A. Quiescent current in
Shutdown mode is less than 1A, which maximizes
battery life.
Mode
Startup and Shutdown State
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.
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 1024s.

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. RT4803A State Chart
Copyright © 2015 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.
DS4803A-00
Augustt 2015
RT4803A
0 : It supports manual reset input (nRST) and interrupt
generation output (nFault).
VOUT
Q3
1 : It is a input of device mode selection.
Fault output (open drain interrupt) : Give a indication if
the fault occurred (OTP, OCP, OVP…).
Q1
LX
Manuel Reset Input : Drive the nRST and nFault. It will
pull low, if the fault occurs.
OCP
The converter senses the current signal when the
Q2
GND
Figure 2. Boost Converter With Bypass Mode
VOUT
high-side P-MOSFET turns on. As a result, the OCP is
cycle by-cycle current limitation. If the OCP occurs, the
converter holds off the next on pulse until inductor
current drops below the OCP limit.
OTP
VIN
The converter has an over-temperature protection.
When the junction temperature is higher than the
thermal shutdown rising threshold, the system will be
latched and the output voltage will no longer be
regulated until the junction temperature drops under the
falling threshold.
EN & nBYP
Figure 3. RT4803A mode changed
Force Pass-Through Mode
It is used to select mode. As the table 1 shown, there
are four device states. When EN and nBYP both pull
high, RT4803A is normal operation and enter automatic
mode.
When EN pulled high and nBYP pulled low. The device
When both EN and nBYP pull low. It enters low IQ
is active in the Force pass-through mode. It supplies
current is approximately 15A typ. From the battery,
the device is short circuit protected by a current limit of
4000mA.
Bypass mode (4A). When the EN pull low and nBYP
pull high, it is forced shut-down and quiescent current is
less than 1A. It works in force pass-through mode, if
the EN pulled high and nBYP pulled low.
VSEL
Discharge
It is concerned the minimum output voltage at the
heavy load condition. There are two output voltage
levels (3.15V & 3.4V) in Boost mode and Bypass mode.
It can be selected by VSET, so it must not be floating.
As the following figures shown, RT4803A features the
discharge function depends on the GPIO. The function
is released when GPIO goes high 2ms later in every
modes but shut down mode.
GPIO
In shut down mode, it is released right away when
GPIO is arranged to be either a mode selection or
nRST/nFault pin. It also be controlled by Reg.0x01[3].
GPIO goes high.
GPIO port configuration bit.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
RT4803A
Table 1
EN input
nBYP input
Device State
0
0
The device is shut down in pass-through mode featuring a low quiescent current
down to ca. 4A typ.
0
1
The device is shut down and the output voltage is reduced to a minimum value.
The device shutdown current is approximately 1A typ.
1
0
The device is active in forced pass-through mode.
The device supply current is approximately 15A 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 50A typ. From the battery
In Shut down Mode (EN = 0, nBYP = 1)
GPIO
Discharge
In Other Modes
GPIO
Discharge
2ms
Figure 4. Discharge Function Diagram
Table 2
EN
nBYP
GPIO
GPIO Pull High 2ms later Discharge
Released Function
Mode
0
0
0
V
FBYP_Low IQ
0
1
0
X
Shut-down
1
0
0
V
FBYP
1
1
0
V
Boost + Auto Bypass
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
6
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
Absolute Maximum Ratings
(Note 1)

VIN, VOUT to AGND -------------------------------------------------------------- 0.2V to 6V

EN, VSEL, GPIO, nBYP to AGND -------------------------------------------- 0.2V to (VIN + 0.2V) w/6V max.

LX --------------------------------------------------------------------------------------  (PGND  0.2V) to (VIN + 0.2V) w/6V max.

Power Dissipation, PD @ TA = 25C

WL-CSP-16B 1.67x1.67 (BSC) ------------------------------------------------- 2.09W

Package Thermal Resistance

WL-CSP-16B 1.67x1.67 (BSC), JA ------------------------------------------- 47.7C/W

Lead Temperature (Soldering, 10 sec.) --------------------------------------- 260C

Junction Temperature ------------------------------------------------------------- 150C

Storage Temperature Range ---------------------------------------------------- 65C to 150C

ESD Susceptibility

HBM (Human Body Model) ------------------------------------------------------ 2kV

MM (Machine Model) -------------------------------------------------------------- 200V
(Note 2)
(Note 3)
Recommended Operating Conditions
(Note 4)

Input Voltage Range ------------------------------------------------------------- 1.8V to 5V

Output Voltage Range ----------------------------------------------------------- 2.85V to 4.4V

Ambient Temperature Range---------------------------------------------------- 40C to 85C

Junction Temperature Range --------------------------------------------------- 40C to 125C
Electrical Characteristics
(VIN = 3V, VOUT = 3.4V, TA = 25C, 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
--
35
--
A
VIN Quiescent Current
IQ
Boost mode, ILOAD = 0mA, Switching,
VIN = 3V
--
55
--
A
VIN Quiescent Current
IQ
Force Bypass with LIQ, VIN = 3.6V
--
4
--
A
VIN Quiescent Current
IQ
Force Bypass without LIQ, VIN = 3.6V
--
15
--
A
VIN Shutdown Current
ISHDN
EN = 0V, nBYP = H, VIN = 3.6V
--
--
1
A
VOUT to VIN Reverse
Leakage
ILK
VOUT = 5V, EN = nBYP = H,
VIN < VOUT
--
0.2
1
A
VOUT Leakage Current
ILK_OUT
VOUT = 0V, EN = 0V, VIN = 4.2V
--
0.1
1
A
VOUT Discharge Impedance
R_DIS_OUT
GPIO = L
--
80
--

Under Voltage Lock Out
VUVLO
VIN Rising
--
1.6
--
V
Under Voltage Lock Out
Hysteresis
VUVLO_HYS
--
200
--
mV
GPIO Low
VGPIO
IGPIO = 5mA
--
--
0.4
V
GPIO Leakage Current
IGPIO_LK
VGPIO = 5V
--
--
1
A
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
7
RT4803A
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Logic Level High EN, VSEL,
nBYP, SCL, SDA, GPIO
VIH
1.2
--
--
V
Logic Level Low EN, VSEL,
nBYP, SCL, SDA, GPIO
VIL
--
--
0.4
V
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
f SW
VIN = 2.65V, VOUT = 3.5V,
ILOAD = 1000mA
--
2.5
--
MHz
Boost Valley Current Limit
ICL
VIN = 2.9V
--
4
--
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
--
45
--
m
P-channel Boost Switch
RDS(ON)
RDSP
VIN = 3.2V, VOUT = 3.5V
--
40
--
m
N-channel Bypass Switch
RDS(ON)
RDSP_BYP
VIN = 3.2V, VOUT = 3.5V
--
35
--
m
Hot Die Trigger Threshold
THD
--
100
--
o
C
Hot Die Release Threshold
THDR
--
90
--
o
Over Temperature Protection
TOTP
--
160
--
o
Over Temperature Protection
Hysteresis
TOTP_HYS
--
20
--
o
FAULT Restart Time
TRST
--
1
--
ms
C
C
C
Note 1. Stresses beyond those listed “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 = 25C 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 © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
8
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
Typical Application Circuit
RT4803A
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 
GPIO
A2
AGND PGND
D1
D2, D3, D4
BOM of Test Board
Reference
Qty.
Part Number
Description
Package
Manufacturer
CIN
1
EMK212ABJ106KG
10F/16V/X5R
0805
Taiyo
COUT
2
LMK212BBJ226MG
22F/10V/X5R
0805
Taiyo
L1
1
DFE2520F-R47M
0.47H
2520
TOKO
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
9
RT4803A
Typical Operating Characteristics
Efficiency vs. Load Current
100
95
95
90
Efficiency (%)
Efficiency (%)
Efficiency vs. Load Current
100
VIN = 2.5V
VIN = 2.7V
85
VIN = 3V
VIN = 3.3V
80
75
VIN = 2.5V
90
VIN = 2.7V
VIN = 3V
85
VIN = 3.3V
80
75
VOUT = 3.4V, ILOAD = 1mA to 2A
70
0.001
VOUT = 3.4V, ILOAD = 100mA to 2A
70
0.01
0.1
1
10
0.1
1
Load Current (A)
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)
80
VIN = 2.5V
90
VIN = 2.7V
VIN = 3V
85
80
75
75
VOUT = 3.15V, ILOAD = 1mA to 2A
VOUT = 3.15V, ILOAD = 100mA to 2A
70
70
0.001
0.01
0.1
1
0.1
10
1
Load Current (A)
10
Load Current (A)
Output Regulation vs. Load Current
Output Regulation vs. Load Current
0.03
0.03
VIN = 2.8V
0.02
Output Regulation (%)1
Output Regulation (%)1
VIN = 2.5V
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 = 3.15V, ILOAD = 0A to 2A
VOUT = 3.4V, 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 © 2015 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.
DS4803A-00
Augustt 2015
RT4803A
Output Ripple vs. Load Current
Output Ripple vs. Load Current
70
70
VOUT = 3.15V, ILOAD = 0A to 2A
VOUT = 3.4V, ILOAD = 0A to 2A
60
Output Rippie (mV)
Output Rippie (mV)
60
50
VIN = 2.5V
40
VIN = 2.7V
30
VIN = 3V
VIN = 3.3V
20
50
VIN = 2.7V
30
VIN = 3V
VIN = 3.1V
20
10
10
0
0
0
500
1000
1500
0
2000
500
1000
1500
2000
Load Current (mA)
Load Current (mA)
Maxiimum Load Current vs. Input Voltage
Startup
5.0
Maximum Load Current (A)1
VIN = 2.5V
40
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 = 3.4V
0.0
2.5
2.7
2.9
3.1
3.3
3.5
3.7
Time (100s/Div)
Input Voltage (V)
Startup
VIN = 3V, VOUT = 3.15V, Load = 50
VIN = 3V, VOUT = 3.4V, Load = 50
Overload Protection
VOUT
(2V/Div)
VIN = 3V, VOUT = 3.4V
VOUT
(2V/Div)
ILX
(1A/Div)
EN
(5V/Div)
ILX
(2A/Div)
PGOOD
(5V/Div)
PGOOD
(5V/Div)
Time (100s/Div)
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
Time (1ms/Div)
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
RT4803A
Load Transient
Overload Protection
VOUT
(200mV/Div)
VOUT
(2V/Div)
ILX
(2A/Div)
PGOOD
(5V/Div)
IOUT
(200mA/Div)
VIN = 3V, VOUT = 3.15V
Time (1ms/Div)
VIN = 3V, VOUT = 3.4V,
ILOAD = 100mA to 500mA
Time (25s/Div)
Load Transient
VOUT
(200mV/Div)
IOUT
(200mA/Div)
VIN = 3V, VOUT = 3.15V,
ILOAD = 100mA to 500mA
Time (25s/Div)
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
12
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
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
≥ VIN = 300mV).
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
0.47H.
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 3.2V, and if
it pulled high, the default is 3.4V.
The output voltage range is from 2.85V to 4.4V.
At least a 10F 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 1F 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 22F 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 RT4803A automatically
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
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
RT4803A
The maximum VRIPPLE occurs when VIN is at
minimum and ILOAD is at maximum.
Output Discharge Function
About this function, it depends on the GPIO pin.
When GPIO pin pull high 2ms later. The function
starts to release but in the shut-down mode. In the
shut-down mode, it is not exist.
This feature prevents residual charge voltages on
capacitor connected to VOUT pins, which may impact
proper power up of the system.
Current Limit
RT4803A 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 5. Inductor Currents In Current Limit Operation
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
14
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
Register Table Lists [Slave address = 1110101 (0x75)]
Name
Address
Description
Silicon Version
0x00
Vendor ID
CONFIG
0x01
MODE control & Spread modulation control
VOUTFLOOR
0x02
Output Voltage Selection
VOUTROOF
0x03
Output Voltage Selection
ILIMSET
0x04
Set current limit & Soft-start current limit
STATUS
0x05
Read IC status
I2C Interface
The RT4803A 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 (RT4803A), P Stop,
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
S Start,
Sr Repeat Start
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
15
RT4803A
Offset 0x00
SILICON VERSION
Bits
7
6
5
4
3
2
1
0
Name
D7
D6
D5
D4
D3
D2
D1
D0
Reset
0
0
0
0
0
0
0
0
Type
RO
RO
RO
RO
RO
RO
RO
RO
1
0
Offset 0x01
CONFIG
Bits
7
6
Name
RESET
Reset
0
0
Type
RW
RW
5
4
3
2
RESERVED
GPIOCFG
SSFM
0
0
0
0
0
1
RW
RW
RW
RW
RW
RW
ENABLE<1> ENABLE<0>
Offset 0x02
Bits
7
MODE_CTRL MODE_CTRL
<1>
<0>
VOUTFLOOR
6
5
Name RESERVED RESERVED RESERVED
4
3
2
1
0
VSEL<4>
VSEL<3>
VSEL<2>
VSEL<1>
VSEL<0>
Reset
0
0
0
0
0
1
1
0
Type
RW
RW
RW
RW
RW
RW
RW
RW
Offset 0x03
Bits
7
VOUTROOF
6
5
Name RESERVED RESERVED RESERVED
4
3
2
1
0
VSEL<4>
VSEL<3>
VSEL<2>
VSEL<1>
VSEL<0>
Reset
0
0
0
0
1
0
1
1
Type
RW
RW
RW
RW
RW
RW
RW
RW
Offset 0x04
Bits
7
ILIMSET
6
Name RESERVED RESERVED
5
4
3
2
1
0
ILIM_OFF
SOFT_START
ILIM<3>
ILIM<2>
ILIM<1>
ILIM<0>
Reset
0
0
0
1
1
1
0
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 © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
16
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
Device ID
Name
Silicon
Version
Bit
Function
Addr
Vendor ID
0x00
name
Reset
Mode
[7:0]
R
D7, D6, D5, D4,
D3, D2, D1, D0
00000000
Name
Function
Addr
CONFIG
MODE control &
Spread modulation
control
0x01
name
Reset
Bit
Mode
7
R/W
RESET
Description
Reversion number
00000 = 1st edition
00001 = 2nd edition
00010 = 3rd edition
00011 = 4th edition
….etc
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
GPIOCFG
0
0 : GPIO port is configured to support manual reset input (nRST)
and interrupt generation output (nFAULT).
1 : GPIO port is configured as a device mode selection input.
2
R/W
SSFM
0
0 : Spread spectrum modulation is disabled.
1 : Spread spectrum modulation is enabled in PWM mode.
01
00 : Device operation follows hardware control signal (GPIO must
be configured as mode selection input).
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).
[1 : 0]
R/W
MODE_CTRL[1 : 0]
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
17
RT4803A
Name
Function
Addr
VOUTFLOOR
Output Voltage
Selection
0x02
name
Reset
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
00110 00100 : VOUT = 3.05V
…
00110 : VOUT = 3.15V (default)
…
11111 : VOUT = 4.4V
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
Description
000
00000 : VOUT = 2.85V
00001 : VOUT = 2.9V
00010 : VOUT = 2.95V
00011 : VOUT = 3V
01011 00100 : VOUT = 3.05V
…
01011 : VOUT = 3.4V (default)
…
11111 : VOUT = 4.4V
Name
Function
Addr
ILIMSET
Set current limit &
Softstart 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]
1101
Description
1000 : 1500mA
1001 : 2000mA
1010 : 2500mA
1011 : 3000mA
1100 : 3500mA
1101 : 4000mA (default)
1110 : 4500mA
1111 : 5000mA
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
18
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
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 © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
19
RT4803A
Thermal Considerations
Layout Consideration
For continuous operation, do not exceed absolute
The PCB layout is an important step to maintain the
high performance of RT4803A.
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 125C. The
junction to ambient thermal resistance, JA, is layout
dependent. For WL-CSP-16B 1.67x1.67 (BSC)
package, the thermal resistance, JA, is 47.7 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 RT4803A 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 RT4803A,
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 = 25C can be
calculated by the following formula :
PD(MAX) = (125C  25C) / (47.7) = 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 6
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 6. Derating Curve of Maximum Power
Dissipation
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
20
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015
RT4803A
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 7. PCB Layout Guide
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS4803A-00
Augustt 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
21
RT4803A
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 © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
22
is a registered trademark of Richtek Technology Corporation.
DS4803A-00
Augustt 2015