GRM31CR71A106KA01 [RICHTEK]
2.25MHz 1A Synchronous Step-Down Converter; 的2.25MHz 1A同步降压转换器
| 型号： | GRM31CR71A106KA01 |
| 厂家： | 
RICHTEK TECHNOLOGY CORPORATION |
| 描述： | 2.25MHz 1A Synchronous Step-Down Converter |
| 文件： | 总11页 (文件大小：224K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
RT8057
2.25MHz 1A Synchronous Step-Down Converter
General Description
Features
z 2.7V to 5.5V Wide Input Operation Range
z 2.25MHz Fixed-Frequency PWM Operation
z Up to 1A Output Current
The RT8057 is a high efficiency Pulse-Width-Modulated
(PWM) step-downDC/DC converter, capable of delivering
1Aoutput current over a wide input voltage range from 2.7V
to 5.5V. The RT8057 is ideally suited for portable electronic
devices that are powered from 1-cell Li-ion battery or from
other power sources such as cellular phones, PDAs, hand-
held devices, game console and related accessories.
z Up to 90% Efficiency
z 0.6V Reference Allows Low Output Voltage
z Internal Soft-Start
z No Schottky Diode Required
z Internal Compensation to Reduce External
Components
The internal synchronous rectifier with low RDS(ON)
dramatically reduces conduction loss at PWM mode.
No external Schottky diode is required in practical
applications. The RT8057 enters LowDropout Mode when
normal Pulse -Width Mode cannot provide regulated output
voltage by continuously turning on the upper P-MOSFET.
The RT8057 enters shut-down mode and consumes less
than 1μA when the EN pin is pulled low. The switching
ripple is easily smoothed-out by small package filtering
elements due to a fixed operating frequency of 2.25MHz.
z Low Dropout Operation : 100% Duty Cycle
z RoHS Compliant and Halogen Free
Applications
z Portable Instruments
z Game Console and Accessories
z Microprocessors and DSP Core Supplies
z Cellular Phones
z Wireless and DSL Modems
z PC Cards
The RT8057 is available in a smallWDFN-6SL2x2 package.
Ordering Information
Pin Configurations
(2)
RT8057
(TOP VIEW)
Taping Type ( Pin1 at Q2)
1
2
3
6
5
4
LX
NC
FB
GND
VIN
EN
Package Type
QW : WDFN-6SL 2x2 (W-Type)
7
Lead Plating System
G : Green (Halogen Free and Pb Free)
WDFN-6SL 2x2
Note :
Marking Information
Richtek products are :
J7 : Product Code
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
W : Date Code
J7W
` Suitable for use in SnPb or Pb-free soldering processes.
DS8057-03 November 2011
www.richtek.com
1
RT8057
Typical Application Circuit
L1
2.2µH
RT8057
1
3
5
V
OUT
2.3V
V
IN
LX
FB
VIN
C
C
IN
4.7µF
OUT
10µF
4
R1
C1
10pF
EN
680k
6, 7 (Exposed Pad)
R2
240k
GND
Function Pin Description
Pin No.
Pin Name
Pin Function
1
2
3
4
5
LX
Switch Node. Connect to the external inductor.
No Internal Connection. Connect to GND.
NC
FB
Feedback Pin. Connect to the external resistor divider.
Chip Enable (Active High).
EN
VIN
Power Input. Connect to the input capacitor.
6,
Power GND. The Exposed Pad must be soldered to a large PCB and connected
to GND for maximum power dissipation.
GND
7 (Exposed Pad)
Function Block Diagram
EN
VIN
R
S1
OSC &
Shutdown
Control
Current
Limit
Detector
Slope
Compensation
Current
Sense
Error
Control
Logic
Driver
Amplifier
FB
LX
PWM
Comparator
R
C
R
S2
COMP
UVLO &
Power Good
Detector
GND
V
REF
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DS8057-03 November 2011
RT8057
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 6.5V
z PowerDissipation, PD @ TA = 25°C
WDFN-6SL 2x2 ------------------------------------------------------------------------------------------------------------ 0.606W
z Package Thermal Resistance (Note 2)
WDFN-6SL 2x2, θJA ------------------------------------------------------------------------------------------------------- 165°C/W
WDFN-6SL 2x2, θJC ------------------------------------------------------------------------------------------------------ 8.2°C/W
z Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM -------------------------------------------------------------------------------------------------------------------------- 2kV
MM---------------------------------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 4)
z Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ 2.7V to 5.5V
z Junction Temperature Range-------------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range-------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 3.6V, TA = 25°C unless otherwise specified)
Parameter
Output Current
Symbol
Test Conditions
= 2.7V to 5.5V
IN
Min
--
Typ
--
Max Unit
I
V
I
1
--
A
OUT
Quiescent Current
IQ
= 0mA
--
81
μA
OUT
−2
−2.5
2
--
2
Reference Voltage
VREF
%
Note 5
Rising
--
2.5
2.4
--
V
2.2
0.2
0.1
2.25
--
V
V
IN
Under Voltage Lockout Threshold V
UVLO
Hysteresis
--
Shutdown Current
ISHDN
--
1
μA
MHz
V
Switching Frequency
--
--
Logic-High
V
V
1
V
IN
IH
IL
EN Threshold
Voltage
Logic-Low
--
--
0.4
--
V
Thermal Shutdown Temperature
T
SD
--
150
250
200
°C
High Side
Switch On
R
R
I
= 0.2A
= 0.2A
--
--
mΩ
mΩ
DS(ON)_H SW
Resistance
Low Side
I
--
--
DS(ON)_L SW
Peak Current Limit
ILIM
1.1
--
1.5
--
2
1
A
%/V
%
Output Voltage Line Regulation
Output Voltage Load Regulation
Start-Up Time
V
= 2.7V to 5.5V
IN
0mA < I
< 0.6A
--
--
1
OUT
t
ss
Guaranteed by Design
200
300
400
μs
DS8057-03 November 2011
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3
RT8057
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 natural convection at TA = 25°C on a low-effective thermal conductivity test board of JEDEC 51-3
thermal measurement standard. The measurement case position of θJC is on the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. The reference voltage accuracy is 2.5% at recommended ambient temperature range, guaranteed by design.
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DS8057-03 November 2011
RT8057
Typical Operating Characteristics
Output Voltage vs. Input Voltage
Efficiency vs. Output Current
2.38
2.36
2.34
2.32
2.30
2.28
2.26
2.24
2.22
100
VIN = 5V
90
80
70
60
50
40
30
20
10
0
VIN = 3.3V
VOUT = 2.3V, IOUT = 0A
VOUT = 2.3V
0.0
0.2
0.4
0.6
0.8
1.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Output Current (A)
Frequency vs. Input Voltage
Frequency vs. Temperature
2.40
2.30
2.25
2.20
2.15
2.10
2.05
2.00
1.95
1.90
2.35
2.30
2.25
2.20
2.15
2.10
2.05
2.00
VIN = 3.3V
VIN = 5V
VIN = 5V, VOUT = 2.3V,
IOUT = 0.2A
VOUT = 2.3V, IOUT = 0.2A
50 75 100 125
2.5
3.0
3.5
4.0
4.5
5.0
5.5
-50
-25
0
25
Input Voltage (V)
Temperature (°C)
Output Current Limit vs. Input Voltage
Output Current Limit vs. Temperature
1.6
1.5
1.4
1.3
1.2
1.1
1.0
1.6
1.5
1.4
1.3
1.2
1.1
1.0
VOUT = 2.3V
VIN = 5V, VOUT = 2.3V
-50
-25
0
25
50
75
100
125
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Temperature (°C)
Input Voltage (V)
DS8057-03 November 2011
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5
RT8057
Reference Voltage vs. Temperature
Output Voltage vs. Temperature
2.35
2.34
2.33
2.32
2.31
2.30
2.29
2.28
2.27
2.26
2.25
0.608
0.606
0.604
0.602
0.600
0.598
0.596
0.594
0.592
VIN = 5V, VOUT = 2.3V,
IOUT = 0A
VIN = 5V, VOUT = 2.3V
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
Output Ripple
Output Ripple
VLX
VLX
(5V/Div)
(5V/Div)
VOUT
(5mV/Div)
VOUT
(5mV/Div)
VIN = 3.3V, VOUT = 2.3V,
IOUT = 1A
VIN = 5V, VOUT = 2.3V, IOUT = 1A
Time (250ns/Div)
Time (250ns/Div)
Load Transient Response
Load Transient Response
VOUT
VOUT
(100mV/Div)
(100mV/Div)
IOUT
IOUT
(500mA/Div)
(500mA/Div)
VIN = 5V, VOUT = 2.3V,
IOUT = 0A to 1A
VIN = 5V, VOUT = 2.3V,
IOUT = 0.4A to 1A
Time (100μs/Div)
Time (100μs/Div)
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DS8057-03 November 2011
RT8057
Power On from EN
Power Off from EN
VIN = 5V, VOUT = 2.3V,
IOUT = 1A
VEN
VEN
(2V/Div)
(2V/Div)
VOUT
VOUT
(2V/Div)
(2V/Div)
IOUT
(500mA/Div)
IOUT
(500mA/Div)
VIN = 5V, VOUT = 2.3V,
IOUT = 1A
Time (100μs/Div)
Time (100μs/Div)
UVLO vs. Temperature
En Threshold vs. Temperature
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
0.80
0.78
0.76
0.74
0.72
0.70
0.68
0.66
0.64
0.62
0.60
Turn On
Turn On
Turn Off
Turn Off
VIN = 5V, VOUT = 2.3V
50 75 100 125
VOUT = 2.3V
75 100 125
-50
-25
0
25
-50
-25
0
25
50
Temperature (°C)
Temperature (°C)
Output Voltage vs. Output Current
2.34
2.33
2.32
2.31
2.30
2.29
2.28
2.27
2.26
VIN = 5V, VOUT = 2.3V
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Output Current (A)
DS8057-03 November 2011
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7
RT8057
Application Information
Low Supply Operation
The basic RT8057 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
The RT8057 is designed to operate down to an input supply
voltage of 2.7V. One important consideration at low input
supply voltages is that the RDS(ON) of the P-Channel and
N-Channel power switches increases. The user should
calculate the power dissipation when the RT8057 is used
at 100% duty cycle with low input voltages to ensure that
thermal limits are not exceeded.
followed by CIN and COUT
.
Output Voltage Setting
The output voltage is set by an external resistive divider
according to the following equation :
R1
Under Voltage Protection (UVP)
VOUT = VREF x (1+
)
R2
Theoutput voltage canbe continuously monitored for under
voltage protection. When the output voltage is less than
33% of its set voltage threshold after OCP occurs, the
under voltage protection circuit will be triggered to auto
re-softstart.
where VREF equals to 0.6V typical. The resistive divider
allows the FB pin to sense a fraction of the output voltage
as shown in Figure 1.
V
OUT
R1
Input Voltage Over Voltage protection (VIN OVP)
FB
RT8057
When the input voltage (VIN) is higher than 6V, VIN OVP
will be triggered and the IC stops switching. Once the
input voltage drops below 6V, the IC will return to normal
operation.
R2
GND
Figure 1. Setting the Output Voltage
Soft-Start
Output Over Voltage Protection (VOUT OVP)
When the output voltage exceeds more than 5% of the
nominal reference voltage, the feedback loop forces the
internal switches off within 50ms. Therefore, the output
over voltage protection is automatically triggered by the
loop.
The RT8057 contains an internal soft-start clamp that
gradually raises the clamp on the FB pin.
100% Duty Cycle Operation
When the input supply voltage decreases toward the output
voltage, the duty cycle increases toward the maximum
on-time. Further reduction of the supply voltage forces
the main switch to remain on for more than one cycle,
eventually reaching 100% duty cycle.
Short Circuit Protection
When the output is shorted to ground, the inductor current
decays very slowly during a single switching cycle. A
current runaway detector is used to monitor inductor
current.As current increases beyond the control of current
loop, switching cycles will be skipped to prevent current
runaway from occurring.
The output voltage will then be determined by the input
voltage minus the voltage drop across the internal
P-MOSFET and the inductor.
Table 1. Inductors
Component
Supplier
Series
Inductance (mH)
2.2mH
DCR (mW)
Current Rating (mA)
Dimensions (mm)
NR4018
T2R2M
TAIYO YUDEN
60
2700
4 X 4 X 1.8
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8
DS8057-03 November 2011
RT8057
CIN and COUT Selection
current handling requirements. Dry tantalum, special
polymer, aluminum electrolytic and ceramic capacitors are
all available in surface mount packages. Special polymer
capacitors offer very low ESR, but have lower capacitance
density than other types. Tantalum capacitors have the
highest capacitance density, but it is important to only use
types that have been surge tested for use in switching
power supplies. Aluminum electrolytic capacitors have
significantly higher ESR, but can be used in cost-sensitive
applications provided that consideration is given to ripple
current ratings and long term reliability. Ceramic capacitors
have excellent low ESR characteristics, but can have a
high voltage coefficient and audible piezoelectric effects.
The input capacitance, CIN, is needed to filter the
trapezoidal current at the source of the top MOSFET. To
prevent large ripple voltage, a low ESR input capacitor
sized for the maximum RMS current should be used. RMS
current is given by :
V
V
IN
OUT
I
= I
- 1
RMS
OUT(MAX)
V
V
OUT
IN
This formula has a maximum at VIN = 2VOUT, where IRMS
=
IOUT/2. This simple worst case condition is commonly used
for design because even significant deviations do not result
in much difference. Choose a capacitor rated at a higher
temperature than required.
The high Q of ceramic capacitors with trace inductance
can also lead to significant ringing.
Several capacitors may also be paralleled to meet size or
height requirements in the design.
Using Ceramic Input and Output Capacitors
The selection of COUT is determined by the effective series
resistance (ESR) that is required to minimize voltage ripple
and load step transients, as well as the amount of bulk
capacitance that is necessary to ensure that the control
loop is stable. Loop stability can be checked by viewing
the load transient response. The output ripple, DVOUT, is
determined by :
Higher value, 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 the 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.
é
ù
ú
1
DV
£ DI ESR +
ê
L
OUT
8fC
ë
OUT û
Theoutputripple is highest at maximuminput voltage since
DIL increases with input voltage. Multiple capacitors placed
in parallel may be needed to meet the ESR and RMS
Table 2. Capacitors for CIN and COUT
Part No. Capacitance (mF)
Component Supplier
MuRata
Case Size
1206
GRM31CR71A475KA01
GRM31CR71A106KA01
4.7mF
10mF
MuRata
1206
DS8057-03 November 2011
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9
RT8057
Thermal Considerations
Layout 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 :
Follow the PCB layout guidelines for optimal performance
of the RT8057.
} Connect the terminal of the input capacitor(s), CIN, as
close as possible to the VIN pin. This capacitor provides
the AC current into the internal power MOSFETs.
} LX node experiences high frequency voltage swing and
should be kept within a small area. Keep all sensitive
small-signal nodes away from the LX node to prevent
stray capacitive noise pick up.
PD(MAX) = (TJ(MAX) - TA) / qJA
whereTJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and qJA is the junction to ambient
thermal resistance.
} Flood all unused areas on all layers with copper. Flooding
with copper will reduce the temperature rise of power
components. Connect the copper areas to any DC net
(VIN, VOUT, GND, or any other DC rail in the system).
For recommended operating condition specifications of
the RT8057, the maximum junction temperature is 125°C
andTA is the ambient temperature. The junction to ambient
thermal resistance, qJA, is layout dependent. For
WDFN-6SL 2x2 packages, the thermal resistance, qJA, is
165°C/W on a standard JEDEC 51-3 single-layer thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
} Connect the FB pin directly to the feedback resistors.
The resistive voltage divider must be connectedbetween
VOUT andGND.
LX should be connected to inductor by
wide and short trace. Keep sensitive
components away from this trace.
C
OUT
PD(MAX) = (125°C - 25°C) / (165°C/W) = 0.606W for
V
OUT
WDFN-6SL 2x2 package
L1
The maximum power dissipation depends on the operating
ambient temperature for fixed TJ(MAX) and thermal
resistance, qJA. For the RT8057 package, the derating
curve in Figure 2 allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
1
2
3
6
5
4
LX
GND
VIN
EN
C
IN
NC
FB
C1
R1
7
V
OUT
Input capacitor must
be placed as close to
R2
the IC as possible.
Figure 3. PCB Layout Guide
0.65
Single-Layer PCB
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 2. Derating Curve for the RT8057 Package
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10
DS8057-03 November 2011
RT8057
Outline Dimension
D2
D
L
E
E2
SEE DETAIL A
1
b
2
1
1
2
e
DETAILA
Pin #1 ID and Tie Bar Mark Options
A
A3
A1
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
A1
A3
b
0.700
0.000
0.175
0.200
1.900
1.550
1.900
0.950
0.800
0.050
0.250
0.350
2.100
1.650
2.100
1.050
0.028
0.000
0.007
0.008
0.075
0.061
0.075
0.037
0.031
0.002
0.010
0.014
0.083
0.065
0.083
0.041
D
D2
E
E2
e
0.650
0.026
0.008
0.012
L
0.200
0.300
W-Type 6SL DFN 2x2 Package
Richtek Technology Corporation
Headquarter
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
5F, No. 95, Minchiuan Road, Hsintien City
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.
DS8057-03 November 2011
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11
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