RT8272
3A, 24V, 1.2MHz Step-Down Converter
General Description
Features
The RT8272 is a high voltage buck converter that can
support the input voltage range from 4.75V to 24V and the
output current can be up to 3A. Current Mode operation
provides fast transient response and eases loop
stabilization.
z
Wide Operating Input Range : 4.75V to 24V
z
Adjustable Output Voltage Range : 0.92V to 15V
Output Current up to 3A
25μ
μA Low Shutdown Current
Power MOSFET : 0.1Ω
Ω
z
z
z
z
The chip provides protection functions such as cycle-bycycle current limiting and thermal shutdown protection.
In shutdown mode, the regulator draws 25μA of supply
current. The RT8272 is available in a SOP-8 (Exposed
Pad) surface mount package.
z
z
z
z
z
Ordering Information
High Efficiency up to 95%
1.2MHz Fixed Switching Frequency
Stable with Low ESR Output Ceramic Capacitors
Thermal Shutdown Protection
Cycle-By-Cycle Over Current Protection
RoHS Compliant and Halogen Free
Applications
RT8272
Package Type
SP : SOP-8 (Exposed Pad-Option 1)
z
Lead Plating System
G : Green (Halogen Free and Pb Free)
z
z
z
Distributive Power Systems
Battery Charger
DSL Modems
Pre-regulator for Linear Regulators
Note :
Pin Configurations
Richtek products are :
`
RoHS compliant and compatible with the current require-
(TOP VIEW)
ments of IPC/JEDEC J-STD-020.
`
BOOT
Suitable for use in SnPb or Pb-free soldering processes.
VIN
2
SW
3
GND
4
GND
9
8
SS
7
EN
6
COMP
5
FB
SOP-8 (Exposed Pad)
Typical Application Circuit
VIN
4.75V to 24V
Chip Enable
2
CIN
10µF
VIN
BOOT
1
RT8272
7 EN
8 SS
CSS
4,
0.1µF
9 (Exposed Pad)
GND
SW 3
CBOOT
L
10nF 4.7µH
D1
B330
R1
25.8k
FB 5
COMP
6
CC
2.2nF
RC
39k
VOUT
3.3V/3A
COUT
47µF
R2
10k
CP
NC
DS8272-02 March 2011
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1
RT8272
Table 1. Recommended Component Selection
VOUT (V)
R1 (kΩ)
R2 (kΩ)
R C (kΩ)
C C (nF)
C OUT (μF)
L (μH)
15
153
10
82
0.82
47
10
10
100
10
62
1.2
47
10
8
77
10
62
1.5
47
6.8
5
43
10
41
2.2
47
6.8
3.3
25.8
10
39
2.2
47
4.7
2.5
17
10
21
2.2
47
4.7
1.8
9.1
10
15
2.2
47
2.2
1.2
3
10
15
2.2
47
2.2
Functional Pin Description
Pin No.
Pin Name
1
BOOT
2
VIN
3
SW
4,
9 (Exposed Pad)
GND
5
FB
6
COMP
7
EN
8
SS
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2
Pin Function
High Side Gate Drive Boost Input. BOOT supplies the drive for the high side
N-MOSFET switch. Connect a 10nF or greater capacitor from SW to BOOT to
power the high side switch.
Power Input. V IN supplies the power to the IC, as well as the step-down converter
switches. Bypass VIN to GND with a suitable large capacitor to eliminate noise on
the input to the IC.
Power Switching Output. SW is the switching node that supplies power to the
output. Connect the output LC filter from SW to the output load. Note that a
capacitor is required from SW to BOOT to power the high side switch.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Feedback Input. FB senses the output voltage to regulate said voltage. The
feedback reference voltage is 0.92V typically.
Compensation Node. COMP is used to compensate the regulation control loop.
Connect a series RC network from COMP to GND to compensate the regulation
control loop. In some cases, an additional capacitor from COMP to GND is
required.
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN
higher than 1.4V to turn on the regulator, lower than 0.4V to turn it off. If the EN
pin is open, it will be pulled to high by internal circuit.
Soft-Start Control Input. SS controls the soft start period. Connect a capacitor
from SS to GND to set the soft-start period. A 0.1μF capacitor sets the soft-start
period to 10ms.
DS8272-02 March 2011
RT8272
Function Block Diagram
VIN
VCC
Internal
Regulator
Oscillator
1.2MHz/440kHz
1µA
EN
10k
3V
VA VCC
Foldback
Control
+
1V
Shutdown
Comparator
VCC
+
UV
Comparator
+
Current
Comparator
z
z
z
z
z
z
z
z
z
z
z
GND
COMP
(Note 1)
Supply Voltage, VIN ----------------------------------------------------------------------------------------- −0.3V to 26V
Switching Voltage, SW ------------------------------------------------------------------------------------- −0.3V to (VIN + 0.3V)
BOOT Voltage ------------------------------------------------------------------------------------------------ (VSW − 0.3V) to (VSW + 6V)
All Other Pins Voltage -------------------------------------------------------------------------------------- −0.3V to 6V
Power Dissipation, PD @ TA = 25°C
SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------- 1.333W
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad), θJA -------------------------------------------------------------------------------- 75°C/W
Junction Temperature --------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------- 260°C
Storage Temperature Range ------------------------------------------------------------------------------- −65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) --------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ---------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
z
SW
+
+EA
Gm = 680µA/V
Absolute Maximum Ratings
z
Logic
0.92V
FB
z
VA
BOOT
0.5V
10µA
SS
Current Sense
Slope Comp Amplifier
+
-
(Note 4)
Supply Voltage, VIN ----------------------------------------------------------------------------------------- 4.75V to 24V
Enable Voltage, VEN ----------------------------------------------------------------------------------------- 0V to 5.5V
Junction Temperature Range ------------------------------------------------------------------------------ −40°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------ −40°C to 85°C
DS8272-02 March 2011
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3
RT8272
Electrical Characteristics
(VIN = 12V, TA = 25°C unless otherwise specified)
Parameter
Symbol
Test Conditions
4.75V ≤ VIN ≤ 24V
Min
Typ
Max
Unit
0.902
0.92
0.938
V
Feedback Reference Voltage
VFB
High Side Switch-On Resistance
RDS(ON)1
--
0.1
0.16
Ω
Low Side Switch-On Resistance
Switch Leakage
RDS(ON)2
VEN = 0V, VSW = 0V
---
10
--
-10
Ω
μA
Current Limit
ILIM
Duty = 80%; VBOOT−SW = 4.8V
--
4.1
--
A
Current Sense Transconductance
GCS
Output Current to VCOMP
--
4
--
A/V
Error Amplifier Tansconductance
Gm
ΔIC = ±10μA
500
680
900
μA/V
Oscillator Frequency
fSW
--
1.2
--
MHz
---
440
80
---
kHz
%
--
90
--
ns
3.8
4.2
4.5
V
--
300
--
mV
--
--
0.4
V
En input High Voltage
1.4
--
--
V
Enable Pull Up Current
0.15
1
2.65
μA
---
25
0.8
-1
μA
mA
--
10
--
μA
--
10
--
ms
--
150
--
°C
Short Circuit Oscillation Frequency
Maximum Duty Cycle
DMAX
Minimum On-Time
Under Voltage Lockout Threshold
Rising
Under Voltage Lockout Threshold
Hysteresis
En input Low Voltage
tON
Shutdown Current
Quiescent Current
ISHDN
IQ
Soft-Start Current
ISS
Soft-Start Period
Thermal Shutdown
VFB = 0V
VFB = 0.8V
VEN = 0V
VEN = 2V, VFB = 1V
CSS = 0.1μF
T SD
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of
JEDEC 51-7 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
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DS8272-02 March 2011
RT8272
Typical Operating Characteristics
Reference Voltage vs. Input Voltage
Efficiency vs. Output Current
0.925
100
VIN = 12V
90
0.924
VIN = 24V
70
Efficiency (%)
Reference Voltage (V)
80
60
50
40
30
20
10
0.923
0.922
0.921
0.920
0.919
0.918
0.917
0.916
VOUT = 3.3V
0.915
0
0
0.5
1
1.5
2
2.5
4
3
6
8
10
Reference Voltage vs. Temperature
16
18
20
22
24
Output Voltage vs. Output Current
0.94
3.350
0.935
3.345
Output Voltage (V)
Reference Voltage (V)
14
Input Voltage (V)
Output Current (A)
0.93
0.925
0.92
0.915
3.340
3.335
3.330
3.325
3.320
3.315
0.91
3.310
0.905
3.305
VIN = 12V
0.9
VIN = 12V
3.300
-50
-25
0
25
50
75
100
0
125
0.5
Temperature (°C)
1
1.5
2
2.5
3
Output Current (A)
Frequency vs. Temperature
Frequency vs. Input Voltage
1.23
1.30
1.22
1.25
Frequency (MHz)1
Frequency (MHz)1
12
1.21
1.20
1.19
1.20
1.15
1.10
1.05
1.18
VOUT = 3.3V, IOUT = 0.3A
VIN = 12V, VOUT = 3.3V, IOUT = 0.3A
1.00
1.17
4
6
8
10
12
14
16
18
Input Voltage (V)
DS8272-02 March 2011
20
22
24
-50
-25
0
25
50
75
100
125
Temperature (°C)
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RT8272
Quiescent Current vs. Temperature
0.90
5.8
0.85
Quiescent Current (mA)
Current Limit (A)
Current Limit vs. Duty Cycle
6.2
5.4
5.0
4.6
4.2
3.8
0.80
0.75
0.70
0.65
3.4
0.60
3.0
0.55
VIN = 12V, VOUT = 3.3V
10
20
30
40
50
60
70
80
-50
-25
0
Duty Cycle (%)
50
75
100
125
Temperature (°C)
UVLO vs. Temperature
Enable Threshold vs. Temperature
1.40
4.8
1.30
4.6
1.20
Enable Threshold (V)
5.0
4.4
UVLO (V)
25
4.2
Rising
4.0
3.8
Falling
3.6
3.4
3.2
Rising
1.10
1.00
Falling
0.90
0.80
0.70
0.60
0.50
3.0
0.40
-50
-25
0
25
50
75
100
125
-50
0
25
50
75
100
Temperature (°C)
Load Transient Response
Load Transient Response
VIN = 12V, VOUT = 3.3V
IOUT = 1.5A to 3A
VOUT
(100mV/Div)
IOUT
(2A/Div)
IOUT
(2A/Div)
Time (100μs/Div)
125
VIN = 12V, VOUT = 3.3V
IOUT = 0A to 3A
VOUT
(50mV/Div)
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6
-25
Temperature (°C)
Time (100μs/Div)
DS8272-02 March 2011
RT8272
Power On from EN Pin
Power Off from EN Pin
VIN = 12V, VOUT = 3.3V
IOUT = 3A
VEN
(5V/Div)
VEN
(5V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
I IN
(500mA/Div)
VIN = 12V, VOUT = 3.3V
IOUT = 3A
Time (2.5ms/Div)
I IN
(500mA/Div)
Time (100μs/Div)
Output Ripple
VOUT
(5mV/Div)
VLX
(10V/Div)
IL
(2A/Div)
VIN = 12V, VOUT = 3.3V
IOUT = 3A
Time (500ns/Div)
DS8272-02 March 2011
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RT8272
Application Information
The RT8272 is an asynchronous high voltage buck
converter that can support the input voltage range from
4.75V to 24V and the output current can be up to 3A.
Output Voltage Setting
The resistive divider allows the FB pin to sense the output
voltage as shown in Figure 1.
Soft-Start
The RT8272 contains an external soft-start clamp that
gradually raises the output voltage. The soft-start timming
can be programed by the external capacitor between SS
pin and GND. The chip provides a 10μA charge current for
the external capacitor. If 0.1μF capacitor is used to set
the soft-start and it’ s period will be 10ms(typ.).
VOUT
Inductor Selection
R1
FB
RT8272
R2
GND
Figure 1. Output Voltage Setting
The output voltage is set by an external resistive divider
according to the following equation :
VOUT = VFB ⎛⎜ 1 + R1 ⎞⎟
⎝ R2 ⎠
Where VFB is the feedback reference voltage (0.92V typ.).
External Bootstrap Diode
Connect a 10nF low ESR ceramic capacitor between the
BOOT pin and SW pin. This capacitor provides the gate
driver voltage for the high side MOSFET.
It is recommended to add an external bootstrap diode
between an external 5V and the BOOT pin for efficiency
improvement when input voltage is lower than 5.5V or duty
ratio is higher than 65%. The bootstrap diode can be a
low cost one such as 1N4148 or BAT54.
The external 5V can be a 5V fixed input from system or a
5V output of the RT8272.
5V
BOOT
RT8272
10nF
SW
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.
V
V
ΔIL = ⎡⎢ OUT ⎤⎥ × ⎡⎢1− OUT ⎤⎥
VIN ⎦
⎣ f ×L ⎦ ⎣
Having a lower ripple current reduces not only the ESR
losses in the output capacitors but also the output voltage
ripple. High frequency with small ripple current can achieve
highest efficiency operation. However, it requires a large
inductor to achieve this goal.
For the ripple current selection, the value of ΔIL = 0.4(IMAX)
will be a reasonable starting point. The largest ripple
current occurs at the highest VIN. To guarantee that the
ripple current stays below the specified maximum, the
inductor value should be chosen according to the following
equation :
⎡ VOUT ⎤ ⎡
VOUT ⎤
L =⎢
⎥ × ⎢1−
⎥
⎣ f × ΔIL(MAX) ⎦ ⎣ VIN(MAX) ⎦
Inductor Core Selection
The inductor type must be selected once the value for L
is known. Generally speaking, high efficiency converters
can not afford the core loss found in low cost powdered
iron cores. So, the more expensive ferrite or
mollypermalloy cores will be a better choice.
The selected inductance rather than the core size for a
fixed inductor value is the key for actual core loss. As the
inductance increases, core losses decrease. Unfortunately,
increase of the inductance requires more turns of wire
and therefore the copper losses will increase.
Figure 2. External Bootstrap Diode
Ferrite designs are preferred at high switching frequency
due to the characteristics of very low core losses. So,
design goals can focus on the reduction of copper loss
and the saturation prevention.
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DS8272-02 March 2011
RT8272
Ferrite core material saturates “hard”, which means that
inductance collapses abruptly when the peak design
current is exceeded. The previous situation results in an
abrupt increase in inductor ripple current and consequent
output voltage ripple.
Do not allow the core to saturate!
Different core materials and shapes will change the size/
current and price/current relationship of an inductor.
Toroid or shielded pot cores in ferrite or permalloy materials
are small and do not radiate energy. However, they are
usually more expensive than the similar powdered iron
inductors. The rule for inductor choice mainly depends
on the price vs. size requirement and any radiated field/
EMI requirements.
Diode Selection
When the power switch turns off, the path for the current
is through the diode connected between the switch output
and ground. This forward biased diode must have a
minimum voltage drop and recovery times. Schottky diode
is recommended and it should be able to handle those
current. The reverse voltage rating of the diode should be
greater than the maximum input voltage, and current rating
should be greater than the maximum load current. For
more detail please refer to Table 3.
CIN and COUT Selection
The input capacitance, C IN, is needed to filter 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
I RMS = I OUT /2. This simple worst-case condition is
commonly used for design because even significant
deviations do not offer much relief.
Choose a capacitor rated at a higher temperature than
required. Several capacitors may also be paralleled to
meet size or height requirements in the design.
For the input capacitor, a 10μF low ESR ceramic capacitor
is recommended. For the recommended capacitor, please
DS8272-02 March 2011
refer to table 2 for more detail. The input capacitor has to
connect another 10μF ceramic capacitor between the input
and ground when the input voltage is lower than 6.5V.
The selection of COUT is determined by the required ESR
to minimize 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 as described in a later section.
The output ripple, ΔVOUT , is determined by :
1
⎤
ΔVOUT ≤ ΔIL ⎡⎢ESR +
8fCOUT ⎥⎦
⎣
The output ripple will be 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. Dry tantalum,
special polymer, aluminum electrolytic and ceramic
capacitors are all available in surface mount packages.
Special polymer capacitors offer very low ESR value.
However, it provides lower capacitance density than other
types. Although Tantalum capacitors have the highest
capacitance density, it is important to only use types that
pass the surge test for use in switching power supplies.
Aluminum electrolytic capacitors have significantly higher
ESR. However, it can be used in cost-sensitive applications
for ripple current rating and long term reliability
considerations. 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.
Higher values, lower 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. However, care must
be taken when these capacitors are used at input and
output. 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.
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RT8272
Checking Transient Response
1.6
Maximum Power Dissipation (W)
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, VOUT immediately shifts by an amount
equal to ΔILOAD (ESR) also begins to charge or discharge
COUT generating a feedback error signal for the regulator
to return VOUT to its steady-state value. During this recovery
time, VOUT can be monitored for overshoot or ringing that
would indicate a stability problem.
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Thermal Considerations
For continuous operation, do not exceed the maximum
operation junction temperature 125°C. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
The maximum power dissipation can be calculated by
following formula :
Four Layer PCB
1.4
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 3. Derating Curves for RT8272 Packages
Layout Consideration
Follow the PCB layout guidelines for optimal performance
of RT8272.
PD(MAX) = ( TJ(MAX) - TA ) / θJA
`
Where T J(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
Keep the traces of the main current paths as short and
wide as possible.
`
Put the input capacitor as close as possible to the device
pins (VIN and GND).
`
LX node is with high frequency voltage swing and should
be kept at small area. Keep analog components away
from the LX node to prevent stray capacitive noise pickup.
`
Connect feedback network behind the output capacitors.
Keep the loop area small. Place the feedback
components near the RT8272.
`
Connect all analog grounds to a command node and
then connect the command node to the power ground
behind the output capacitors.
`
An example of PCB layout guide is shown in Figure 4
for reference.
For recommended operating conditions specification of
RT8272, where the maximum junction temperature is
125°C. The junction to ambient thermal resistance θJA is
layout dependent. For SOP-8 (Exposed Pad) packages,
the thermal resistance θJA is 75°C/W on the standard
JEDEC 51-7 four-layers thermal test board. The maximum
power dissipation at TA = 25°C can be calculated by
following formula:
PD(MAX) = (125°C − 25°C) / (75°C/W) = 1.333W for
SOP-8 (Exposed Pad) packages
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. For RT8272 packages, the Figure 3 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
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DS8272-02 March 2011
RT8272
GND
VIN
SW
CSS
CB
VIN
2
SW
3
6
The parallel distance between
COMP and FB traces must be
SS
as short as possible.
EN
CC
COMP
GND
4
5
FB
CIN
Input capacitor must be placed
as close to the IC as possible.
BOOT
D1
C OUT
The output capacitor must be
VOUT
placed near the RT8272.
L
8
GND
7
CP
RC
GND
SW should be connected to inductor by
wide and short trace. Keep sensitive
components away from this trace.
VOUT
The resistor divider must be connected
as close to the device as possible.
Figure 4. PCB Layout Guide
Table 2. Suggested Inductors for Typical Application Circuit
Component Supplier
Series
Inductance (µH)
DCR (mΩ)
Current Rating (A)
Dimensions (mm)
TDK
RLF7030
4.7
31
3.5
7.3 x 6.8 x 3.2
TAIYO YUDEN
NR8040
4.7
18
4.7
8x8x4
GOTERND
GSSR2
4.7
18
5.7
10 x 10 x 3.8
Table 3. Suggested Capacitors for CIN and COUT
Component Supplier
Part No.
Capacitance (µF)
Case Size
MURATA
GRM31CR61E106K
10
1206
TDK
C3225X5R1E106K
10
1206
TAIYO YUDEN
TMK316BJ106ML
10
1206
MURATA
GRM31CR60J476M
47
1206
TDK
C3225X5R0J476M
47
1210
TAIYO YUDEN
EMK325BJ476MM
47
1210
Table 4. Suggested Diode
Component Supplier
Series
VRRM (V)
IOUT (A)
Package
DIODES
B330A
30
3
DO-214AC
DIODES
B340
40
3
DO-214AB
PANJIT
SK33
30
3
DO-214AB
PANJIT
SK34
40
3
DO-214AB
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11
RT8272
Outline Dimension
H
A
M
EXPOSED THERMAL PAD
(Bottom of Package)
Y
J
X
B
F
C
I
D
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
4.801
5.004
0.189
0.197
B
3.810
4.000
0.150
0.157
C
1.346
1.753
0.053
0.069
D
0.330
0.510
0.013
0.020
F
1.194
1.346
0.047
0.053
H
0.170
0.254
0.007
0.010
I
0.000
0.152
0.000
0.006
J
5.791
6.200
0.228
0.244
M
0.406
1.270
0.016
0.050
X
2.000
2.300
0.079
0.091
Y
2.000
2.300
0.079
0.091
X
2.100
2.500
0.083
0.098
Y
3.000
3.500
0.118
0.138
Option 1
Option 2
8-Lead SOP (Exposed Pad) Plastic Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: marketing@richtek.com
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
www.richtek.com
12
DS8272-02 March 2011