®
RT8088A
2.7MHz 3A Step-Down Converter with I
2
C Interface
General Description
The RT8088A is a full featured 5.5V, 3A, Constant-On-
Time (COT) synchronous step-down converter with two
integrated MOSFETs. The current mode COT operation
with internal compensation allows the transient response
to be optimized
over a wide range of loads and output
capacitors to efficiently reduce external component count.
The RT8088A provides up to 2.7MHz switching frequency
to minimize the size of output inductor and capacitors.
The output voltage is programmed through an I
2
C interface
capable of operating up to 400kHz.
The RT8088A is available in the WL-CSP-15B 1.31x2.11
(BSC) package.
Features
2.5V to 5.5V Input Voltage Range
Current Mode COT Control Loop Design
Fast Transient Response
Internal 48mΩ and 22mΩ Synchronous Rectifier
Ω
Ω
I
2
C compatible interface up to 400kHz
Highly Accurate V
OUT
Regulation Over Load/Line
Range
Robust Loop Stability with Low-ESR C
OUT
RoHS Compliant and Halogen Free
Applications
Distributed Power Systems
Enterprise Servers, Ethernet Switches & Routers, and
Global Storage Equipment
Telecom & Industrial Equipment
Ordering Information
RT8088A
Package Type
WSC : WL-CSP-15B 1.31x2.11 (BSC)
Note :
Richtek products are :
½
Pin Configurations
(TOP VIEW)
PVIN
PVIN
PVIN
AVIN
A1
A2
A3
PGND
PGND
PGND
SDA
FB
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.
LX
B1
C1
B2
B3
C3
LX
C2
½
PGND
D1
D2
D3
Marking Information
1J : Product Code
EN
AGND
E1
E2
E3
SCL
1JW
W : Date Code
WL-CSP-15B 1.31x2.11 (BSC)
Simplified Application Circuit
RT8088A
V
IN
…
PVDD
AVDD
Enable
I C
Control
2
LX
FB
PGND
AGND
V
OUT
EN
SDA
SCL
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8088A-01 August 2017
www.richtek.com
1
RT8088A
Functional Pin Description
Pin No.
A1, B1, C1
A2, B2
Pin Name
PVIN
LX
Input Supply Voltage, 2.5V to 5.5V.
Switch Node. The Source of the internal high-side power MOSFET, and Drain of
the internal low-side (synchronous) rectifier MOSFET.
Power Ground.
Analog Circuit Input Supply Voltage.
Enable Control Input. Pull high to enable.
I C Data Signal.
Analog Ground Should be Electrically Connected to GND Close to the Device.
I C Clock Signal.
Feedback Voltage Input.
2
2
Pin Function
A3, B3, C2, C3 PGND
D1
D2
D3
E1
E2
E3
AVIN
EN
SDA
AGND
SCL
FB
Function Block Diagram
EN
AVIN
UVLO
OTP
Shutdown
Control
TON
Comparator
+
-
R
C
LX
PVIN
FB
Error Amplifier
+
-
+
0.8V
Logic
Control
Current
Limit
Detector
Current
Sense
AZC
Driver
LX
V
REF
SDA
SCL
2
C
COMP
I C Control
LX
PGND
LX
AGND
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8088A-01 August 2017
RT8088A
Operation
The RT8088A is a low voltage synchronous step-down
converter that can support the input voltage range from
2.5V to 5.5V and the output current can be up to 3A. The
RT8088A uses a constant on-time, current mode
architecture. In steady-state operation, the high-side P-
MOSFET is turned on when the current feedback reaches
COMP level which is the amplified difference between the
reference voltage and the feedback voltage. The on-time
of high-side P-MOSFET is determined by on-time
generator which is a function of input and output voltage.
After on-time expires, high-side MOSFET is turned off
and low-side MOSFET is turned on. Until the low-side
current sensing signal reaches the COMP, the high-side
MOSFET is turned on again. In this manner, the converter
regulates the output voltage and keeps the frequency
constant.
The RT8088A reduces the external component count by
integrating the boot recharge MOSFET.
The error amplifier EA adjusts COMP voltage
by comparing
the output voltage with the internal I
2
C set reference voltage.
When the load increases, it causes a drop in the output
relative to the reference, then the
COMP voltage rises to
allow higher inductor current to match the load current.
PWM Frequency and Adaptive On-Time Control
The on-time can be roughly estimated by the equation :
V
1
T
ON
=
OUT
V
IN
f
SW
where f
SW
is nominal 3MHz
Auto-Zero Current Detector
The auto-zero current detector circuit senses the LX
waveform to adjust the zero current threshold voltage.
When the current of low-side MOSFET decreases to the
zero current threshold, the low-side MOSFET turns off to
prevent negative inductor current. In this way, the zero
current threshold can adjust for different condition to get
better efficiency.
Under-Voltage Lockout (UVLO)
The UVLO continuously monitors the VCC voltage to make
sure the device works properly. When the VCC is high
enough to reach the UVLO high threshold voltage, the
step-down converter softly starts or pre-bias to its regulated
output voltage. When the VCC decreases to its UVLO
low threshold voltage, the device will shut down.
Power Good
When the output voltage is higher than PGOOD rising
threshold, the PGOOD flag is high.
Output Under-Voltage Protection (UVP)
When the output voltage is lower than 0.4V after soft-
start, the UVP is triggered. The system will be latched
and the output voltage will no longer be regulated during
UVP latched state. Re-start input voltage or EN pin can
unlatch the protection state. Using I
2
C to shutdown the
system and then re-enable it will also unlatch UVP function.
Over-Current Protection (OCP)
The RT8088A senses the current signal when the low-
side MOSFET turns on. As a result, The OCP is cycle-
by-cycle limit. If the OCP occurs, the converter holds off
the next on pulse until inductor current drops below the
OCP limit.
Soft-Start
An internal current source charges an internal capacitor
to build the soft-start ramp voltage. The typical soft start
time is 150μs.
Over-Temperature Protection (OTP)
The RT8088A has an over-temperature protection. When
the device triggers the OTP, the system will be latched
and the output voltage will no longer be regulated during
OTP latched state. Re-start input voltage or EN pin can
unlatch the protection state. Using I
2
C to shutdown the
system and then re-enable it will also unlatch UVP function.
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8088A-01 August 2017
www.richtek.com
3
RT8088A
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6.5V
−0.3V
to (V
IN
+ 0.3V)
2W
49.8°C/W
150°C
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------
Other Pins ------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
WL-CSP-15B 1.31x2.11 (BSC) ---------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
WL-CSP-15B 1.31x2.11 (BSC),
θ
JA
----------------------------------------------------------------------------
Junction Temperature ----------------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C
Storage Temperature Range -------------------------------------------------------------------------------------
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) --------------------------------------------------------------------------------------- 2kV
Recommended Operating Conditions
(Note 4)
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------
2.5V to 5.5V
Junction Temperature Range -------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 3.7V, T
A
= 25°C, unless otherwise specified)
Parameter
Under-Voltage Lockout
Threshold
Shutdown Supply Current
Quiescent Current
Voltage Reference
Soft-Start Time
Enable Input
Voltage
Switch
On-Resistance
Logic-High
Logic-Low
High-Side
Low-Side
Symbol
V
UVLO
I
SHDN
I
Q
V
REF
t
SS
V
EN_H
V
EN_L
R
ONH
R
ONL
I
CL
T
S
f
OSC
Rising
Falling
Test Conditions
V
CC
Rising
EN = 0V
Active, V
SENSE
= 0.9V, No Switching
At any set point, with a load from 0
to 3A and over input voltage range
Min
--
--
--
2
--
1.05
--
--
--
Typ
2.35
1
75
--
--
--
--
48
22
3.9
150
2.7
Max
--
5
100
2
150
--
0.4
--
--
--
--
--
Unit
V
A
A
%
s
V
m
A
C
MHz
Current Limit Threshold
Thermal Shutdown Threshold
Switching Frequency
Valley Current, IPEAK [1:0] = 11
--
--
--
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8088A-01 August 2017
RT8088A
Parameter
Resolution
DAC Step Size
Minimum VOUT
EN, SDA and SCL High
EN, SDA and SCL Low
EN, SDA and SCL Current
Symbol
R
ES
V
DAC
V
DACMIN
D
HIGH
D
LOW
D
CURRENT
Test Conditions
Default V
OUT
= 1.225V
(Register 1100100)
Min
7
--
--
1.05
--
--
Typ
--
6.25
600
--
--
--
Max
--
--
--
--
0.4
0.1
Unit
Bits
mV
mV
V
V
mA
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.
θ
JA
is measured at T
A
= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
Note 3.
Devices are ESD sensitive. Handling precaution is recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8088A-01 August 2017
www.richtek.com
5
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