RICHTEK RT8058A

RT8058A
1.2MHz, 2A, High Efficiency PWM Step-Down
DC/DC Converter
General Description
Features
The RT8058A is a current mode PWM step-down converter.
The chip is ideal for fixed frequency and low ripple
applications over full range of load conditions. Its input
voltage range is from 2.6V to 5.5V with a constant 1.2MHz
switching frequency that allows it to adopt tiny, low cost
capacitors and inductors with 2mm or less in height making
it ideal for single-cell Li-lon/polymer battery applications.
The low on resistance internal MOSFET can achieve high
efficiency without the need of external schottky diodes in
wide operating ranges and the output voltage is adjustable
from 0.6V to 5V that can provide up to 2A load current.
The RT8058A operates at 100% duty cycle for low dropout
operation that extends battery life in portable devices.
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The RT8058A is available in a WDFN-10L 3x3 package.
Ordering Information
RT8058A
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Applications
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Package Type
QW : WDFN-10L 3x3 (W-Type)
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
0.6V Reference Allows Low Output Voltage
Low Dropout Operation : 100% Duty Cycle
2A Load Current
<2μ
μA Shutdown Current
Up to 95% Efficiency
No Schottky Diode Required
1.2MHz Constant Switching Frequency
Low RDS(ON) Internal Switches
Internally Compensated
Internal Soft-Start
Over temperature Protection
Short Circuit Protection
Small 10-Lead WDFN Package
RoHS Compliant and Halogen Free
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Portable Instruments
Microprocessors and DSP Core supplies
Cellular Telephones
Wireless and DSL Modems
Digital Cameras
PC Cards
Note :
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RoHS compliant and compatible with the current require-
Pin Configurations
(TOP VIEW)
ments of IPC/JEDEC J-STD-020.
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Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
E9= : Product Code
E9=YM
DNN
YMDNN : Data Code
DS8058A-02 April 2011
PGND
PGND
FB
GND
POK
1
2
3
4
5
GND
11
10
9
8
7
9
Richtek products are :
LX
LX
PVDD
VDD
EN
WDFN-10L 3x3
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1
RT8058A
Typical Application Circuit
RT8058A
8 PVDD
VIN
2.6V to 5.5V
6 EN
C1
10µF
R3
100k
C2
1µF
7 VDD
5 POK
PGOOD
GND
4
LX
9, 10
L1
3.3µH
VOUT
1.2V/2A
R1
100k
FB
3
C3
22µF
PGND
1, 2,
11 (Exposed Pad)
C4
1µF
R2
100k
Functional Pin Description
Pin No.
Pin Name
Pin Function
1, 2,
Power Ground. Connect this pin close to the (–) terminal of C IN and C OUT. Exposed
PGND
11 (Exposed Pad)
pad should be soldered to PCB board and connected to GND.
Feedback Input Pin. Receives the feedback voltage from a resistive divider
3
FB
connected across the output.
Signal Ground. Return the feedback resistive dividers to this ground, which in turn
4
GND
connects to PGND at one point.
Power Good Indicator. Open-drain logic output that is opened when the output
5
POK
voltage exceeds 90% of the regulation point.
Enable pin. A logical high level at this pin enables the converter, while a logical low
6
EN
level causes the converter to shut down.
Signal Input Supply. Decouple this pin to GND with a capacitor. Normally VDD is
7
VDD
equal to PVDD.
Power Input Supply of converter power stage. Decouple this pin to PGND with a
8
PVDD
capacitor.
Internal Power MOSFET Switches Output of converter. Connect this pin to the
9, 10
LX
inductor.
Function Block Diagram
PVDD
Current Sense
Slope
Com
OSC
0.6V
FB
EA
Output
Clamp
OC
Limit
Driver
Int-SS
0.3V
LX
Control
Logic
UV
PGND
VREF
0.533V
OTP
GND
POK
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2
POR
VDD
EN
DS8058A-02 April 2011
RT8058A
Absolute Maximum Ratings
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(Note 1)
Supply Input Voltage VDD, PVDD ------------------------------------------------------------------------------------LX Pin Switch Voltage ---------------------------------------------------------------------------------------------------Other I/O Pin Voltage ----------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------------WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------
Recommended Operating Conditions
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−0.3V to 6V
−0.3V to 6V
−0.3V to 6V
1.429W
70°C/W
7.8°C/W
260°C
−65°C to 150°C
150°C
2kV
200V
(Note 4)
Supply Input Voltage ------------------------------------------------------------------------------------------------------ 2.6V to 5.5V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VDD = VPVDD = 3.6V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Input Voltage Range
VIN
Feedback Reference Voltage
VREF
DC Bias Current
(PVDD, VDD total)
Under voltage Lockout
Threshold
UVLO
Test Conditions
Min
Typ
Max
Unit
2.6
--
5.5
V
0.582
0.6
0.618
V
Active, No Load
--
3.4
--
mA
Active, Not Switching, V FB = 0.5V
--
340
--
μA
Shutdown, EN = 0
--
--
2
μA
2.3
2.43
2.55
V
VDD Hysteresis
--
150
--
mV
Switching Frequency
1
1.2
1.4
MHz
VDD Rising
Oscillator Frequency
fOSC
EN High-Level Input Voltage
VEN_H
1.4
--
--
V
EN Low-Level Input Voltage
VEN_L
--
--
0.4
V
Switch On Resistance, High
RDS(ON)_P
IOUT = 200mA
--
142
210
mΩ
Switch On Resistance, Low
RDS(ON)_N
IOUT = 200mA
--
96
160
mΩ
Peak Current Limit
ILIM
2.2
3
--
A
Output Voltage Line Regulation
VIN = 2.6V to 5.5V, IOUT = 0
--
0.05
--
%/V
Output Voltage Load
IOUT = 0AÆ2A
--
1
--
%/A
DS8058A-02 April 2011
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RT8058A
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. The case point 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.
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DS8058A-02 April 2011
RT8058A
Typical Operating Characteristics
Efficiency vs. Output Current
Output Voltage vs. Output Current
100
1.196
90
VIN = 3.3V
70
1.194
Output Voltage (V)
Efficiency (%)
1.195
VIN = 5V
80
60
50
40
30
20
1.193
VIN = 5V
1.192
VIN = 3.3V
1.191
1.190
1.189
10
VOUT = 1.2V, L = 3.3μH, COUT = 22μF
0
0
0.25
0.5
0.75
1
1.25
1.5
1.75
VOUT = 1.2V, L = 3.3μH, COUT = 22μF
1.188
2
0
0.25
0.5
Output Current (A)
1
1.25
1.5
1.75
2
FB Voltage vs. Temperature
0.600
1.199
0.598
1.198
0.596
1.197
0.594
FB Voltage (V)
Output Voltage (V)
Output Voltage vs. Input Voltage
1.200
1.196
1.195
1.194
1.193
0.592
0.590
0.588
0.586
0.584
1.192
0.582
1.191
IOUT = 0A
1.190
2.5
3
3.5
4
4.5
5
VIN = 3.3V, IOUT = 0A
0.580
-50
5.5
-25
0
Switching Frequency vs. Input Voltage
1.35
1.35
Switching Frequency (MHz)
1.40
1.30
1.25
1.20
1.15
1.10
1.05
VOUT = 1.2V, IOUT = 300mA
2.5
3
3.5
4
4.5
Input Voltage (V)
DS8058A-02 April 2011
50
75
100
125
Switching Frequency vs. Temperature
1.40
1.00
25
Temperature (°C)
Input Voltage (V)
Switching Frequency (MHz)
0.75
Output Current (A)
5
5.5
1.30
1.25
1.20
1.15
1.10
1.05
VIN = 3.3V, VOUT = 1.2V, IOUT = 300mA
1.00
-50
-25
0
25
50
75
100
125
Temperature (°C)
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RT8058A
EN Voltage vs. Input Voltage
EN Voltage vs. Temperature
1.4
1.4
1.3
1.3
Rising
1.2
1.1
1.0
EN Voltage (V)
EN Voltage (V)
1.2
Falling
0.9
0.8
0.7
0.6
1.1
Rising
1.0
0.9
Falling
0.8
0.7
0.6
0.5
0.5
VOUT = 1.2V, IOUT = 0A
0.4
2.5
3
3.5
4
4.5
5
VIN = 3.3V, VOUT = 1.2V, IOUT = 0A
0.4
-50
5.5
-25
0
Output Current vs. Input Voltage
50
75
100
125
Output Current vs. Temperature
3.2
3.2
3.1
3.1
3.0
3.0
Output Current (A)
Output Current (A)
25
Temperature (°C)
Input Voltage (V)
2.9
2.8
2.7
2.6
2.5
2.9
2.8
2.7
2.6
2.5
2.4
2.4
2.3
VOUT = 1.2V
2.2
2.5
3
3.5
4
4.5
5
5.5
2.3
VIN = 3.3V, VOUT = 1.2V
2.2
-50
Load Transient Response
25
50
75
100
125
VIN = 3.3V, VOUT = 1.2V, IOUT = 10mA to 2A
VOUT
(50mV/Div)
VOUT
(50mV/Div)
IOUT
(1A/Div)
IOUT
(1A/Div)
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0
Load Transient Response
VIN = 3.3V, VOUT = 1.2V, IOUT = 10mA to 1A
Time (50μs/Div)
-25
Temperature (°C)
Input Voltage (V)
Time (50μs/Div)
DS8058A-02 April 2011
RT8058A
Load Transient Response
Load Transient Response
VIN = 5V, VOUT = 1.2V, IOUT = 10mA to 1A
VIN = 5V, VOUT = 1.2V, IOUT = 10mA to 2A
VOUT
(50mV/Div)
VOUT
(50mV/Div)
IOUT
(1A/Div)
IOUT
(1A/Div)
Time (50μs/Div)
Time (50μs/Div)
Output Ripple Voltage
Output Ripple Voltage
VIN = 3.3V, VOUT = 1.2V, IOUT = 2A
VIN = 3.3V, VOUT = 1.2V, IOUT = 0A
VOUT
(10mV/Div)
VOUT
(10mV/Div)
VLX
(5V/Div)
VLX
(5V/Div)
Time (500ns/Div)
Time (500ns/Div)
Output Ripple Voltage
Output Ripple Voltage
VIN = 5V, VOUT = 1.2V, IOUT = 0A
VIN = 5V, VOUT = 1.2V, IOUT = 2A
VOUT
(10mV/Div)
VOUT
(10mV/Div)
VLX
(5V/Div)
VLX
(5V/Div)
Time (500ns/Div)
DS8058A-02 April 2011
Time (500ns/Div)
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RT8058A
Power On from EN
Power On from EN
VIN = 3.3V, VOUT = 1.2V, IOUT = 0A
VIN = 3.3V, VOUT = 1.2V, IOUT = 2A
VEN
(2V/Div)
VEN
(2V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
IOUT
(2A/Div)
IOUT
(2A/Div)
100μs/Div)
Time (100μs/Div)
Power On from VIN
Power On from VIN
VIN = 3.3V, VOUT = 1.2V, IOUT = 2A
VEN = 3.3V, VOUT = 1.2V, IOUT = 0A
VIN
(2V/Div)
VIN
(2V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
IOUT
(2A/Div)
IOUT
(2A/Div)
Time (500μs/Div)
Time (500μs/Div)
Power Off from EN
Power Off from EN
VIN = 5V, VOUT = 1.2V, IOUT = 2A
VIN = 3.3V, VOUT = 1.2V, IOUT = 2A
VEN
(2V/Div)
VEN
(2V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
IOUT
(2A/Div)
IOUT
(2A/Div)
Time (500μs/Div)
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Time (500μs/Div)
DS8058A-02 April 2011
RT8058A
Application Information
Function Description
The RT8058A is a 1.2MHz constant frequency, current
mode PWM step-down converter. High switching frequency
and high efficiency make it suitable for applications where
high efficiency and small size are critical.
The output voltages are set by external dividers returned
to the FB pin. The output voltage can be set from 0.6V to
5V.
The resistive divider allows the FB pin to sense a fraction
of the output voltage as shown in Figure 1.
V OUT
R1
FB
RT8058A
R2
GND
Figure 1. Setting the Output Voltage
Main Control Loop
During normal operation, the internal top power switch
(P-MOSFET) is turned on at the beginning of each clock
cycle. Current in the inductor increases until the peak
inductor current reach the value defined by the output
voltage of the error amplifier. The error amplifier adjusts its
output voltage by comparing the feedback signal from a
resistor divider on the FB pin with an internal 0.6V
reference. When the load current increases, it causes a
reduction in the feedback voltage relative to the reference.
The error amplifier raises its output voltage until the average
inductor current matches the new load current. When the
top power MOSFET shuts off, the synchronous power
switch (N-MOSFET) turns on until the beginning of the
next clock cycle.
Soft-Start / Enable
For convenience of power up sequence control, the
RT8058A has an enable pin. Logic high at EN pin will
enable the converter. When the converter is enabled, the
clamped error amplifier output ramps up during 1024-clock
period to increase the current provided by converter until
the output voltage reach the target voltage. If EN is kept
at high during VIN applying, the RT8058A will be enabled
when VDD surpass Under Voltage Lockout threshold.
Output Voltage Programming
The output voltage is set by an external resistive divider
according to the following equation :
VOUT = VREF x (1+ R1/R2)
where VREF equals to 0.6V typical.
DS8058A-02 April 2011
Slope Compensation and Inductor Peak Current
Slope compensation provides stability in constant
frequency architectures by preventing sub harmonic
oscillations at duty cycles greater than 50%. It is
accomplished internally by adding a compensating ramp
to the inductor current signal. Normally, the maximum
inductor peak current is reduced when slope compensation
is added. In RT8058A, however, separated inductor current
signal is used to monitor over current condition and this
keeps the maximum output current relatively constant
regardless of duty cycle.
Dropout Operation
When 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. The output voltage
will then be determined by the input voltage minus the
voltage drop across the internal P-MOSFET and the
inductor.
Low Supply Operation
The RT8058A is designed to operate down to an input
supply voltage of 2.6V. 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
RT8058A is used at 100% duty cycle with low input
voltages to ensure that thermal limits are not exceeded.
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RT8058A
Short Circuit Protection
At overload condition, current mode operation provides
cycle-by-cycle current limit to protect the internal power
switches. When the output is shorted to ground, the
inductor current will decays very slowly during a single
switching cycle. A current runaway detector is used to
monitor inductor current. As current increasing beyond
the control of current loop, switching cycles will be skipped
to prevent current runaway from occurring. If the FB voltage
is smaller than 0.3V after the completion of soft-start
period, Under Voltage Protection (UVP) will lock the output
to high-z to protect the converter. UVP lock can only be
cleared by recycling the input power.
Thermal Protection
If the junction temperature of the RT8058A reaches certain
temperature (150°C), both converters will be disabled. The
RT8058 will be re-enabled and automatically initializes
internal soft start when the junction temperature drops
below 110 °C.
Inductor Selection
For a given input and output voltage, the inductor value
and operating frequency determine the ripple current. The
ripple current ΔIL increases with higher VIN and decreases
with higher inductance.
⎡V
⎤ ⎡ V
⎤
ΔIL = ⎢ OUT ⎥ × ⎢1 − OUT ⎥
f
L
×
V
IN ⎦
⎣
⎦ ⎣
Having a lower ripple current reduces the ESR losses in
the output capacitors and the output voltage ripple. Highest
efficiency operation is achieved at low frequency with small
ripple current. This, however, requires a large inductor. A
reasonable starting point for selecting the ripple current
is ΔIL = 0.4(IMAX). The largest ripple current occurs at
the highest VIN. To guarantee that the ripple current stays
below a specified maximum, the inductor value should be
chosen according to the following equation :
⎡ VOUT ⎤ ⎡
VOUT ⎤
L=⎢
⎥
⎥ × ⎢1 − V
f
I
×
Δ
L(MAX) ⎦ ⎣
IN(MAX) ⎦
⎣
Inductor Core Selection
Once the value for L is known, the type of inductor must
be selected. High efficiency converters generally cannot
afford the core loss found in low cost powdered iron cores,
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forcing the use of more expensive ferrite or mollypermalloy
cores. Actual core loss is independent of core size for a
fixed inductor value but it is very dependent on the
inductance selected. As the inductance increases, core
losses decrease. Unfortunately, increased inductance
requires more turns of wire and therefore copper losses
will increase.
Ferrite designs have very low core losses and are preferred
at high switching frequencies, so design goals can
concentrate on copper loss and preventing saturation.
Ferrite core material saturates “hard”, which means that
inductance collapses abruptly when the peak design
current is exceeded. This result 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 don' t radiate energy but generally cost more
than powdered iron core inductors with similar
characteristics. The choice of which style inductor to use
mainly depends on the price vs. size requirements and
any radiated field/EMI requirements.
CIN and COUT Selection
The input capacitance, C IN, 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 :
IRMS = IOUT(MAX)
VOUT
VIN
VIN
−1
VOUT
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 offer much relief. Note that ripple current ratings from
capacitor manufacturers are often based on only 2000
hours of life which makes it advisable to further derate the
capacitor, or 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.
DS8058A-02 April 2011
RT8058A
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 as described in a later section.
The output ripple, ΔVOUT, is determined by :
⎡
1 ⎤
ΔVOUT ≤ ΔIL ⎢ESR +
8fCOUT ⎥⎦
⎣
The output ripple is highest at 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 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 high Q of ceramic capacitors with trace inductance
can also lead to significant ringing.
Using Ceramic Input and Output Capacitors
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 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.
DS8058A-02 April 2011
Checking Transient Response
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), where ESR is the effective series
resistance of COUT. ΔILOAD also begins to charge or
discharge COUT generating a feedback error signal used
by 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.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature. 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 :
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.
For recommended operating conditions specification of
RT8058A, The maximum junction temperature is 125°C.
The junction to ambient thermal resistance θJA is layout
dependent. For WDFN-10L 3x3 packages, the thermal
resistance θJA is 70°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) / (70°C/W) = 1.429W for
WDFN-10L 3x3 packages
The maximum power dissipation depends on operating
ambient temperature for fixed T J(MAX) and thermal
resistance θJA. For RT8058A packages, the Figure 2 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
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Maximum Power Dissipation (W)
RT8058A
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
is not used, the signal and power grounds should be
segregated with all small-signal components returning
to the GND pin at one point that is then connected to
the PGND pin close to the IC. The exposed pad should
be connected to GND.
Four Layers PCB
WDFN-10L 3x3
0
25
50
75
100
`
Connect the terminal of the input capacitor(s), as close
as possible to the PVDD pin. This capacitor provides
the AC current into the internal power MOSFETs.
`
LX node is with high frequency voltage swing and should
be kept small area. Keep all sensitive small-signal nodes
away from LX node to prevent stray capacitive noise
pick-up.
`
Flood all unused areas on all layers with copper.
Flooding with copper will reduce the temperature rise
of power components. The copper areas can be
connectde to any DC net (PVDD, VDD, VOUT, PGND,
GND, or any other DC rail in your system).
`
Connect the FB pin directly to the feedback resistors.
The resistor divider must be connected between VOUT
and GND.
125
Ambient Temperature (°C)
Figure 2. Derating Curves for RT8058A Package
Layout Considerations
Follow the PCB layout guidelines for optimal performance
of RT8058A.
A ground plane is recommended. If a ground plane layer
The feedback
components must be
connected as close to
the device as possible.
PGND
PGND
R1
FB
GND
R2
POK
V OUT
C OUT
L1
1
10
2
9
3
GND
5
8
7
4
11
9
`
LX
LX
PVDD
VDD
EN
LX should be connected
to inductor by wide and
short trace. Keep
sensitive components
away from this trace.
C IN V IN
Input capacitor must be placed as
close to the IC as possible.
Figure 3. PCB Layout Guide
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12
DS8058A-02 April 2011
RT8058A
Table 1. Recommended Inductors
Component
Series
Supplier
T AIYO YUDEN
NR 4018
Murata
LQH66S
TDK
SLF7045T
Sumida
CDRH5D16
GOTREND
GTSD53
Inductance
(µH)
3.3
3.3
3.3
3.3
3.3
DCR
(mΩ)
70
22
20
36
34
Current Rating
(m A)
2000
2600
2500
2600
2360
Dimensions
(mm)
4 x 4 x 1.8
6.3 x 6.3 x 4.7
7 x 7 x 4.5
5.8 x 5.8 x 1.8
5 x 5 x 2.8
Table 2. Recommended Capacitors for CIN and COUT
Component Supplier
Part No.
Capacitance (µF)
Case Size
TDK
C3225X5R0J226M
22
1210
TDK
C2012X5R0J106M
10
0805
Panasonic
ECJ4YB1A226M
22
1210
Panasonic
ECJ4YB1A106M
10
1210
TAIYO YUDEN
LMK325BJ226ML
22
1210
TAIYO YUDEN
JMK316BJ226ML
22
1206
TAIYO YUDEN
JMK212BJ106ML
10
0805
DS8058A-02 April 2011
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13
RT8058A
Outline Dimension
D2
D
L
E
E2
1
e
SEE DETAIL A
b
2
1
2
1
A
A1
A3
DETAIL A
Pin #1 ID and Tie Bar Mark Options
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
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
2.950
3.050
0.116
0.120
D2
2.300
2.650
0.091
0.104
E
2.950
3.050
0.116
0.120
E2
1.500
1.750
0.059
0.069
e
L
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 10L DFN 3x3 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: [email protected]
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.
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14
DS8058A-02 April 2011