RT8088A - Richtek

®
RT8088A
2.7MHz 3A Step-Down Converter with I2C Interface
General Description
Features
The RT8088A is a full featured 5.5V, 3A, Constant-OnTime (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 3MHz switching frequency
to minimize the size of output inductor and capacitors.
The RT8088A is available in the WL-CSP-15B 1.31x2.11
(BSC) package.
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2.5V to 5.5V Input Voltage Range
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Current Mode COT Control Loop Design
Fast Transient Response
Internal 48mΩ
Ω and 22mΩ
Ω Synchronous Rectifier
Highly Accurate VOUT Regulation Over Load/Line
Range
Robust Loop Stability with Low-ESR COUT
RoHS Compliant and Halogen Free
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Applications
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Ordering Information
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RT8088A
Package Type
WSC : WL-CSP-15B 1.31x2.11 (BSC)
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Distributed Power Systems
Enterprise Servers, Ethernet Switches & Routers, and
Global Storage Equipment
Telecom & Industrial Equipment
Pin Configurations
Note :
Richtek products are :
`
(TOP VIEW)
RoHS compliant and compatible with the current requirePVIN
ments of IPC/JEDEC J-STD-020.
`
A1
A2
A3
PGND
B3
PGND
C3
PGND
D3
SDA
E3
FB
LX
Suitable for use in SnPb or Pb-free soldering processes.
PVIN
B1
B2
LX
PVIN
C1
Marking Information
AVIN
D1
1J : Product Code
1JW
C2
PGND
D2
EN
AGND
W : Date Code
E1
E2
SCL
WL-CSP-15B 1.31x2.11 (BSC)
Simplified Application Circuit
RT8088A
VIN
…
Enable
2
I C
Control
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8088A-00 October 2013
PVDD
LX
AVDD
FB
EN
PGND
SDA
SCL
AGND
VOUT
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1
RT8088A
Functional Pin Description
Pin No.
A1, B1, C1
A2, B2
Pin Name
Pin Function
PVIN
Input Supply Voltage, 2.5V to 5.5V.
LX
Switch Node. The Source of the internal high-side power MOSFET, and Drain of
the internal low-side (synchronous) rectifier MOSFET.
A3, B3, C2, C3 PGND
Power Ground.
D1
AVIN
Analog Circuit Input Supply Voltage.
D2
EN
Enable Control Input. Pull high to enable.
D3
SDA
I C Data Signal.
E1
AGND
Analog Ground Should be Electrically Connected to GND Close to the Device.
E2
SCL
I C Clock Signal.
E3
FB
Feedback Voltage Input.
2
2
Function Block Diagram
EN
UVLO
Shutdown
Control
OTP
FB
AVIN
TON
Error Amplifier
+
+
0.8V
Comparator
+
-
Logic
Control
LX
PVIN
Driver
LX
RC
VREF
SDA
SCL
CCOMP
2
I C Control
Current
Limit
Detector
Current
Sense
AZC
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2
LX
PGND
LX
AGND
is a registered trademark of Richtek Technology Corporation.
DS8088A-00 October 2013
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 PMOSFET 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 I2C 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
TON = OUT ×
where fSW is nominal 3MHz
V
f
IN
SW
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.
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8088A-00 October 2013
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 softstart, 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 I2C 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 lowside MOSFET turns on. As a result, The OCP is cycleby-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 I2C to shutdown the
system and then re-enable it will also unlatch UVP function.
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3
RT8088A
Absolute Maximum Ratings
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(Note 1)
Supply Input Voltage, VIN ---------------------------------------------------------------------------------------Other Pins -----------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
WL-CSP-15B 1.31x2.11 (BSC) --------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WL-CSP-15B 1.31x2.11 (BSC), θJA ---------------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------
Recommended Operating Conditions
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−0.3V to 6.5V
−0.3V to (VIN + 0.3V)
2W
49.8°C/W
150°C
260°C
−65°C to 150°C
2kV
(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
(VIN = 3.7V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Under-Voltage Lockout
Threshold
VUVLO
VCC Rising
--
2.35
--
V
Shutdown Supply Current
ISHDN
EN = 0V
--
1
5
μA
Quiescent Current
IQ
Active, VSENSE = 0.9V, No Switching
--
75
100
μA
Voltage Reference
VREF
At any set point, with a load from 0
to 3A and over input voltage range
−2
--
2
%
Soft-Start Time
tSS
--
--
150
μs
Enable Input
Voltage
Switch
On-Resistance
Logic-High
VEN_H
Rising
1.05
--
--
Logic-Low
VEN_L
Falling
--
--
0.4
High-Side
RONH
--
48
--
Low-Side
RONL
--
22
--
--
3.9
--
A
Valley Current, IPEAK [1:0] = 11
V
mΩ
Current Limit Threshold
ICL
Thermal Shutdown Threshold
TS
--
150
--
°C
Switching Frequency
fOSC
--
2.7
--
MHz
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DS8088A-00 October 2013
RT8088A
Parameter
Symbol
Test Conditions
Default VOUT = 1.225V
(Register 1100100)
Min
Typ
Max
Unit
7
--
--
Bits
Resolution
RES
DAC Step Size
VDAC
--
6.25
--
mV
Minimum VOUT
VDACMIN
--
600
--
mV
EN, SDA and SCL High
DHIGH
1.05
--
--
V
EN, SDA and SCL Low
DLOW
--
--
0.4
V
EN, SDA and SCL Current
DCURRENT
--
--
0.1
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. θJA 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 is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8088A-00 October 2013
is a registered trademark of Richtek Technology Corporation.
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5
RT8088A
Typical Application Circuit
VIN
Remote
47µF
…
A1, B1, C1
4.7µF
Enable
2
I C
Control
D1
AVDD
D2 EN
D3 SDA
E2
SCL
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RT8088A
PVDD
LX
FB
PGND
A2, B2
0.33µH
E3
VOUT
22µF
A3, B3, C2, C3
AGND E1
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DS8088A-00 October 2013
RT8088A
Typical Operating Characteristics
Efficiency vs. Output Current
Output Voltage vs. Input Voltage
100
1.26
90
1.25
Efficiency (%)
70
Output Voltage (V)
80
VIN = 3V
VIN = 3.7V
VIN = 4.2V
60
50
40
30
1.24
1.23
IOUT = 0A
IOUT = 3A
IOUT = 1A
1.22
1.21
1.2
20
1.19
10
VOUT = 1.225V, L = 0.33μH
0
0.001
VOUT = 1.225V
1.18
0.01
0.1
1
3
10
3.5
4
Output Current (A)
5
1.25
1.25
1.24
1.24
1.23
1.22
VIN = 5.5V
VIN = 3.7V
VIN = 3V
1.20
1.19
1.23
VIN = 4.2V
VIN = 3.7V
VIN = 3V
1.22
1.21
1.20
1.19
VOUT = 1.225V
IOUT = 1A
1.18
1.18
-50
-25
0
25
50
75
100
125
0
0.5
1
1.5
2
2.5
3
Output Current (A)
Temperature (°C)
Frequency vs. Input Voltage
Frequency vs. Temperature
3.0
3.0
2.9
2.9
Frequency (MHz)
Frequency (MHz)
5.5
Output Voltage vs. Output Current
1.26
Output Voltage (V)
Output Voltage (V)
Output Voltage vs. Temperature
1.26
1.21
4.5
Input Voltage (V)
2.8
2.7
2.6
2.5
2.4
2.8
2.7
2.6
2.5
2.4
VOUT = 1.225V, IOUT = 1A
2.3
VIN = 3.7V, VOUT = 1.225V, IOUT = 1A
2.3
2.5
3
3.5
4
4.5
5
Input Voltage (V)
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8088A-00 October 2013
5.5
-50
-25
0
25
50
75
100
125
Temperature (°C)
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7
RT8088A
Output Current Limit vs. Input Voltage
UVLO Voltage vs. Temperature
5.0
2.50
2.40
4.0
UVLO Voltage (V)
Output Current Limit (A)
2.45
4.5
IPEAK <1:0>=11
3.5
IPEAK <1:0>=10
3.0
IPEAK <1:0>=01
2.5
2.35
Rising
2.30
2.25
2.20
2.15
Falling
2.10
2.05
VOUT = 1.225V
2.0
VOUT = 1.225V, IOUT = 0A
2.00
3
3.5
4
4.5
5
5.5
-50
-25
0
25
50
75
100
125
Temperature (°C)
Input Voltage (V)
EN Threshold vs. Input Voltage
EN Threshold vs. Temperature
1.0
1.4
1.3
1.2
EN Threshold (V)
EN Threshold (V)
0.9
0.8
Rising
0.7
0.6
1.1
1.0
0.9
0.8
Rising
0.7
0.6
Falling
VOUT = 1.225V, IOUT = 0A
0.5
Falling
0.5
VIN = 3.7V, VOUT = 1.225V, IOUT = 0A
0.4
2.5
3
3.5
4
4.5
5
5.5
-50
0
25
50
75
100
Temperature (°C)
Load Transient Response
Load Transient Response
VOUT
(20mV/Div)
VOUT
(20mV/Div)
IOUT
(2A/Div)
IOUT
(2A/Div)
VIN = 3.7V, VOUT = 1.225V,
IOUT = 10mA to 3A, L = 0.33μH
Time (50μs/Div)
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8
-25
Input Voltage (V)
125
VIN = 3.7V, VOUT = 1.225V,
IOUT = 1A to 3A, L = 0.33μH
Time (50μs/Div)
is a registered trademark of Richtek Technology Corporation.
DS8088A-00 October 2013
RT8088A
Output Ripple Voltage
Output Ripple Voltage
VIN = 3.7V, VOUT = 1.225V, IOUT = 10mA, L = 0.33μH
VIN = 3.7V, VOUT = 1.225V, IOUT = 1A, L = 0.33μH
VOUT
(5mV/Div)
VOUT
(10mV/Div)
VLX
(2V/Div)
VLX
(2V/Div)
Time (10μs/Div)
Time (250ns/Div)
Power On from VIN
Power Off from VIN
VIN = 3.7V, VOUT = 1.225V, IOUT = 3A
VIN = 3.7V, VOUT = 1.225V, IOUT = 3A
VIN
(5V/Div)
VIN
(5V/Div)
VLX
(5V/Div)
VLX
(5V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
I IN
(2A/Div)
I IN
(2A/Div)
Time (2.5ms/Div)
Time (5ms/Div)
Power On from EN
Power Off from EN
VIN = 3.7V, VOUT = 1.225V, IOUT = 3A
VEN
(2V/Div)
VEN
(2V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
VLX
(5V/Div)
VLX
(5V/Div)
I IN
(2A/Div)
I IN
(2A/Div)
VIN = 3.7V, VOUT = 1.225V, IOUT = 3A
Time (25μs/Div)
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8088A-00 October 2013
Time (25μs/Div)
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RT8088A
Application Information
The basic RT8088A application circuit is shown in Typical
Application Circuit. External component selection is
determined by the maximum load current and begins with
the selection of the inductor value and operating frequency
followed by CIN and COUT.
Inductor Selection
The inductor value and operating frequency determine the
ripple current according to a specific input and output
voltage. The ripple current, ΔIL, increases with higher VIN
and decreases with higher inductance, as shown in
equation below :
⎤
⎡V
⎤ ⎡ V
ΔIL = ⎢ OUT ⎥ x ⎢1− OUT ⎥
VIN ⎦
⎣ fxL ⎦ ⎣
where f is the operating frequency and L is the inductance.
Having a lower ripple current reduces not only the ESR
losses in the output capacitors, but also the output voltage
ripple. Higher operating frequency combined with smaller
ripple current is necessary to achieve high efficiency. Thus,
a large inductor is required to attain this goal. The largest
ripple current occurs at the highest VIN. To guarantee that
the ripple current stays below the specified ΔIL(MAX), the
inductor value should be chosen according to the following
equation :
⎡ VOUT
⎤ ⎡
⎤
V
L=⎢
⎥ x ⎢1− OUT ⎥
⎢⎣ f x ΔIL(MAX) ⎥⎦ ⎢⎣ VIN(MAX) ⎥⎦
The inductor's current rating (defined by a temperature
rise from 25°C ambient to 40°C) should be greater than
the maximum load current and its saturation current should
be greater than the short-circuit peak current limit. Refer
to Table 1 for the suggested inductor selection.
Table 1. Suggested Inductors for Typical
Application Circuit
Component
Supplier
CYNTEC
Part Number
PIFE20161BR33MS-39
Dimensions
(mm)
An input capacitor, C IN, is needed to filter out the
trapezoidal current at the source of the high-side MOSFET.
To prevent large ripple current, a low ESR input capacitor
sized for the maximum RMS current should be used. The
RMS current is given by :
IRMS = IOUT(MAX)
VOUT
VIN
VIN
−1
VOUT
This formula has a maximum at VIN = 2VOUT, where IRMS =
IOUT(MAX)/2. This simple worst-case condition is commonly
used for design. Choose a capacitor rated at a higher
temperature than required. Several capacitors may also
be paralleled to meet the size or height requirements of
the design. Ceramic capacitors have high ripple current,
high voltage rating and low ESR, which makes them ideal
for switching regulator applications. However, they can
also have a high voltage coefficient and audible
piezoelectric effects. The high Q of ceramic capacitors
with trace inductance can lead to significant ringing. When
a ceramic capacitor is used at the input and the power is
supplied by a wall adapter through long wires, a load step
at the output can induce ringing at the input, VIN. At best,
this ringing can couple to the output and be mistaken as
loop instability. At worst, a sudden inrush of current
through the long wires can potentially cause a voltage
spike at VIN large enough to damage the part. Thus, care
must be taken to select a suitable input capacitor.
The selection of COUT is determined by the required ESR
to minimize output voltage ripple. Moreover, the amount
of bulk capacitance is also a key for COUT selection to
ensure that the control loop is stable. Loop stability can
be checked by viewing the load transient response. The
output voltage ripple, ΔVOUT, is determined by :
⎡
⎤
1
ΔVOUT ≤ ΔIL ⎢ESR +
⎥
8fOSCCOUT ⎦
⎣
2.0 X 1.6 X 1.2
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Input and Output Capacitor Selection
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DS8088A-00 October 2013
RT8088A
where fOSC is the switching frequency and ΔIL is the
inductor ripple current. The output voltage ripple will be
the highest at the maximum input voltage since ΔIL
increases with input voltage. Multiple capacitors placed in
parallel may be needed to meet the ESR and RMS current
handling requirement. Ceramic capacitors have excellent
low ESR characteristics, but can have a high voltage
coefficient and audible piezoelectric effects. The high Q
of ceramic capacitors with trace inductance can also lead
to significant ringing. Nevertheless, high value, low cost
ceramic capacitors are now becoming available in smaller
case sizes. Their high ripple current, high voltage rating
and low ESR make them ideal for switching regulator
applications.
I2C Interface Function
RT8088A can be used by I2C interface to select Vout
voltage level, peak current limit level, thermal warning
temperature level, PWM control mode, and so on. The
register of each function can be found from the following
register map and it also explains how to use these function.
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
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RT8088A
I2C Interface
The RT8088A I2C slave address = 7'b0011100.
I2C Register Map
Register
b[7]
Register Address
Name
(MSB)
b[6]
b[5]
b[4]
b[3]
b[2]
SEN_
TSD
SEN_
TWARN
SEN_
TPREW
Default
0
0
0
0
0
0
0
0
Read/Write
R
R
R
R
R
R
R
R
b[2]
b[1]
b[0]
(LSB)
RESV
SEN_PG
SEN_TSD
0 : Junction temperature below thermal shutdown (150°C) limit
1 : Junction temperature above thermal shutdown (150°C) limit
SEN_TWARN
0 : Junction temperature below thermal shutdown (135°C) limit
1 : Junction temperature above thermal shutdown (135°C) limit
SEN_TPREW
0 : Junction temperature below thermal shutdown (105°C) limit
1 : Junction temperature above thermal shutdown (105°C) limit
RESV
Reserved bits
0 : DCDC output voltage below target
1 : DCDC output voltage within nominal range
SEN_PG
Register
b[7]
Register Address
Name
(MSB)
b[6]
b[5]
Meaning
PRODUCT_ID
0
0
1
0
1
0
1
Read/Write
R
R
R
R
R
R
R
R
b[5]
b[4]
b[3]
b[2]
b[1]
b[0]
(LSB)
PRODUCT_ID
b[7]
(MSB)
b[6]
Meaning
REVISION_ID
Default
0
0
0
0
0
0
0
1
Read/Write
R
R
R
R
R
R
R
R
b[6]
b[5]
b[4]
b[3]
b[2]
b[1]
b[0]
(LSB)
REVISION_ID
Register
Register Address
Name
REVISION_ID
b[7]
(MSB)
Meaning
FEATURE_ID
Default
0
0
0
0
0
0
0
0
Read/Write
R
R
R
R
R
R
R
R
FEATURE_ID
FEATURE_ID
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12
b[3]
0
Register
Register Address
Name
FEATURE
0x05
_ID
b[4]
Default
PRODUCT_ID
REVISION
0x04
_ID
b[0]
(LSB)
Meaning
MONITOR 0x01
PRODUCT
0x03
_ID
b[1]
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RT8088A
Register
Name
PROG
Register
Address
b[5]
b[4]
b[3]
b[2]
b[1]
b[0]
(LSB)
EN
Default
1
1
1
0
0
1
0
0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
VOLT_SEL
b[1]
b[0]
(LSB)
0 : Disabled
1 : Enabled
EN
VID Table satisfy :
SEL [6:0] = 1111111 : VOUT = 1393.75mV
...
SEL [6:0] = 1100100 : VOUT = 1.225V (default)
...
SEL [6:0] = 0000000 : VOUT = 0.6V
6.25mV step for DCDC, VOUT = 600mV + 6.25mV x SEL
VOLT_SEL
Register
Address
b[7]
(MSB)
Meaning
DISCHARGE 0x12
b[6]
b[5]
RESV
b[4]
b[3]
b[2]
DISCHG
RESV
Default
0
0
0
0
0
0
0
0
Read/Write
R
R
R
R/W
R
R
R
R
b[4]
b[3]
b[2]
b[1]
b[0]
(LSB)
RESV
Reserved bits
0 : discharge path disabled
1 : discharge path enabled
DISCHG
RESV
Register
Name
b[6]
Meaning
0x11
Register
Name
b[7]
(MSB)
Reserved bits
Register
Address
b[7]
(MSB)
b[6]
b[5]
Meaning
PWM
RESV
DVSMODE
Default
0
0
0
0
0
0
0
0
Read/Write
R/W
R
R/W
R
R
R
R
R
COMMAND 0x14
PWM
0 : Auto
1 : Forced PWM
RESV
Reserved bits
DVSMODE
RESV
0 : Auto DVS transition mode
1 : Forced PWM DVS transition
Reserved bits
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8088A-00 October 2013
RESV
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
13
RT8088A
Register
Name
Register
Address
Meaning
LIMCONF 0x16
b[6]
IPEK <1:0>
b[4]
b[3]
b[2]
TPWTH <1:0>
b[1]
b[0]
(LSB)
RESV
1
1
1
0
0
0
1
1
Read/Write
R/W
R/W
R/W
R/W
R
R
R
R
TPWTH <1:0>
00 : 2.9A
01 : 2.9A
10 : 3.4A
11 : 3.9A
00 : 83°C
01 : 94°C
10 : 105°C
11 : 116°C
Reserved bits
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
www.richtek.com
14
b[5]
Default
IPEAK <1:0>
RESV
b[7]
(MSB)
is a registered trademark of Richtek Technology Corporation.
DS8088A-00 October 2013
Thermal Considerations
For continuous operation, do not exceed absolute
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) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA 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, θJA, is layout dependent. For
Maximum Power Dissipation (W)1
RT8088A
4.0
Four-Layer PCB
3.2
2.4
1.6
0.8
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 1. Derating Curve of Maximum Power Dissipation
WL-CSP-15B 1.31x2.11 (BSC) package, the thermal
resistance, θJA, is 49.8°C/W on a standard JEDEC 51-7
four-layer thermal test board. The maximum power
dissipation at TA = 25°C can be calculated by the following
formula :
P D(MAX) = (125°C − 25°C) / (49.8°C/W) = 2W for
WL-CSP-15B 1.31x2.11 (BSC) package
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 1 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
Copyright © 2013 Richtek Technology Corporation. All rights reserved.
DS8088A-00 October 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
15
RT8088A
Outline Dimension
Symbol
Dimensions In Millimeters
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
2.060
2.160
0.081
0.085
D1
E
1.600
1.260
0.063
1.360
0.050
0.054
E1
0.800
0.031
e
0.400
0.016
15B WL-CSP 1.31x2.11 Package (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.
www.richtek.com
16
DS8088A-00 October 2013