1MHz, 2A, High Efficiency PWM Step-Down DC/DC Converter
General Description
The RT8058 is a current mode PWM step-down converter.
The chip is ideal for fixed frequency and low ripple
applicati
ons over full range of load conditions. Its input
voltage range is from 2.6V to 5.5V with a constant 1MHz
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 RT8058 operates at 100% duty cycle for low dropout
operation that extends battery life in portable devices.
The RT8058 is available in a WQFN-16L 3x3 package.
Ordering Information
RT8058
Package Type
QW : WQFN-16L 3x3 (W-Type)
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
Features
zz
0.6V Reference Allows Low Output Voltage
z
zz
zz
z Low Dropout Operation : 100% Duty Cycle
zz
zz
z 2A Load Current
zz
μμ
zz
z <2
μA Shutdown Current
zz
μμ
zz
z Up to 95% Efficiency
zz
zz
z No Schottky Diode Required
zz
zz
z 1MHZ Constant Switching Frequency
zz
zz
z Low R
zz
zz
z Internally Compensated
zz
zz
z Internal Soft-Start
zz
zz
z Over temperature Protection
zz
zz
z Short Circuit Protection
zz
zz
z Small 16-Lead WQFN Package
zz
zz
z RoHS Compliant and 100% Lead (Pb)-Free
zz
Internal Switches
DS(ON)
Applications
z Portable Instruments
z Microprocessors and DSP Core supplies
z Cellular Telephones
z Wireless and DSL Modems
z Digital Cameras
z PC Cards
Pin Configurations
(TOP VIEW)
NC
LXLXLX
13141516
PVDD
NC
17
EN
12
11
PVDD
10
PVDD
VDD
9
8765
NC
PGND
PGND
PGND
FB
1
2
PGND
3
4
GND
WQFN-16L 3x3
DS8058-05 April 2011www.richtek.com
1
RT8058
Typical Application Circuit
L1
3.3µH
V
2.6V to 5.5V
IN
C
IN
10µF
10,11,12
7
9
RT8058
PVDD
EN
VDD
GND
5
13,14,15
LX
4
FB
PGND
1, 2, 3,
Exposed Pad (17)
Functional Pin Description
Pin No. Pin Name Pin Function
1, 2, 3
17 (Expos ed Pad)
PGND
4 FB
5 GND
6, 8, 16 NC No Internal Connection.
7 EN
9 VD D
10, 11 , 1 2 PV DD
13, 14, 15 LX
Power Ground. Connect this pin close to the (–) terminal of C
exposed pad must be soldered to a large PCB and connected to PGND for
maximum power dissipation.
Feedback Input Pin. Receives the feedback voltage from a resistive divider
connected across the output.
Signal Ground. Return the feedback resistive dividers to this ground, which in turn
connects to PGND at one point.
Enable pin. A logical high level at this pin enables the converter, while a logical
low level causes the converter to shut down.
Signal Input Supply. Decouple this pin to GND wi th a capacitor. Normally VDD is
equal to PVDD. Keep the voltage difference between VDD and PVDD less than
0.5V.
Power Input Supply of converter power stage. Decouple this pin to PGND with a
capacitor.
Internal Power MOSFET Switches Output of converter. Connect this pin to the
inductor.
R1
100k
R2
100k
C
OUT1
22µF
C
OUT2
22µF
V
OUT
1.2V/2A
and C
IN
OUT
. The
Function Block Diagram
0.6V
FB
EA
Int-SS
2
Output
Clamp
0.3V
OSC
VREF
Slope
Com
POR
VDD
Control
Logic
EN
ISEN
OC
Limit
OT
Temp-SEN
PVDD
Driver
LX
PGND
GND
DS8058-05 April 2011www.richtek.com
RT8058
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage VDD, PVDD ------------------------------------------------------------------------------------- −0.3V to 6V
z LX Pin Switch Voltage ---------------------------------------------------------------------------------------------------- −0.3V to 6V
z Other I/O Pin Voltage ----------------------------------------------------------------------------------------------------- −0.3V to 6V
z Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions (Note 4)
z Supply Input Voltage ------------------------------------------------------------------------------------------------------ 2.6V to 5.5V
z Junction Temperature Range --------------------------------------------------------------------------------------------
z Ambient Temperature Range --------------------------------------------------------------------------------------------
@ TA = 25°C
D
−40°C to 125°C
−40°C to 85°C
Electrical Characteristics
(V
= V
DD
Input Voltage Range
Feedback Voltage
DC Bias Current
(PVDD, VDD total)
Under voltage Lockout
Threshold
Oscillator Frequency
EN High-Level Input Voltage
EN Low-Level Input Voltage
Switch On Resistance, High R
Switch On Resistance, Low R
Peak Current Limit I
Output Voltage Line Regulation
Output Voltage Load Regulation
PVDD
= 3.6V, T
= 25°C, unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
V
IN
V
FB
UVLO
f
OSC
V
EN_H
V
EN_L
DS(ON)_P
DS(ON)_N
LIM
2.6 - - 5.5 V
0.582 0.6 0.618 V
Active, No Load -- 3.4 -- mA
Active, Not Switching, VFB = 0.5V
Shutdown, EN = 0 -- -- 2
VDD Rising
Hysteresis
V
DD
Switching Frequency
1.4 -- -- V
-- -- 0.4 V
I
I
= 200mA
OUT
= 200mA -- 96 160 mΩ
OUT
-- 340 -- μA μA
2.3 2.43 2.55 V
-- 150 -- mV
0.75 1.0 1.25 MHz
--
142 210 mΩ
2.2 3 -- A
V
= 2.6V to 5.5V
IN
I
= 0AÆ2A
LOAD
-- 0.05 -- %/V
--
0.15 -- %/A
DS8058-05 April 2011www.richtek.com
3
RT8058
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. θ
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of
JA
JEDEC 51-7 thermal measurement standard. The case point of θ
is on the exposed pad of the package.
JC
DS8058-05 April 2011www.richtek.com
4
Typical Operating Characteristics
RT8058
1.2000
1.1998
1.1996
1.1994
1.1992
1.1990
1.1988
1.1986
Output Voltage (V)
1.1984
1.1982
1.1980
Efficiency vs. Output Current
100
90
80
70
60
50
40
Efficiency (%)
30
20
10
0
0500100015002000
V
= 1.8V, L = 3.3μH, C
OUT
OUT
Output Current (mA)
Output Voltage vs. Outout Current
VIN = 5V
VIN = 3.3V
0250500750 1000 1250 1500 1750 2000
Outout Current (mA)
VIN = 5V
VIN = 3.3V
= 22μFx2
0.6010
0.6008
0.6006
0.6004
0.6002
0.6000
0.5998
0.5996
0.5994
Reference Voltage (V)
0.5992
0.5990
Efficiency vs. Output Current
100
90
80
70
60
50
40
Efficiency (%)
30
20
10
0
0500100015002000
V
= 1.2V, L = 3.3μH, C
OUT
OUT
Output Current (mA)
Reference Voltage vs. Input Voltage
2.73.13.53.94.34.75.15.5
Input Voltage (V)
VIN = 5V
VIN = 3.3V
= 22μFx2
Output Voltage vs. Temperature
1.205
1.203
1.201
1.199
1.197
1.195
1.193
1.191
Output Voltage (V)
1.189
1.187
1.185
-50-250255075100125
Temp erature
(°C)
VIN = 3.6V
1100
1050
1000
950
Frequency (kHz)
900
850
-50-250255075100125
Frequency vs. Temperature
VIN = 3.6V, V
Temp erature
= 1.2V, I
OUT
(°C)
OUT
= 0A
DS8058-05 April 2011www.richtek.com
5
RT8058
Quiescent Current vs. Input Voltage
450
400
350
300
Quiescent Current (uA)
250
2.73.13.53.94.34.75.15.5
Input Voltage(V)
Peak Cu rrent limit vs. Input Voltage
3.3
3.2
Quiescent Current v s. Temperature
450
400
350
300
Quiescent Current (uA)
250
-50-250255075100125
Temp erature
(°C)
VIN = 3.6V
Peak Cu rrent limit vs. Temperature
3.5
3.3
3.1
3.0
Peak Current limit (A)
2.9
2.8
V
OUT
(50mV/Div)
I
OUT
(1A/Div)
V
= 1.2V
OUT
2.73.13.53.94.34.75.15.5
Input Voltage (V)
Load Transient Response
V
= 3.3V, V
IN
OUT
= 1.2V, I
= 0A to 1A
OUT
Peak Current limit (A)
V
OUT
(50mV/Div)
I
OUT
(1A/Div)
3.1
2.9
2.7
2.5
-50-250255075100125
Temperature
VIN = 3.6V, V
(°C)
OUT
= 1.2V
Load Transient Response
V
= 3.3V, V
IN
OUT
= 1.2V, I
= 0A to 2A
OUT
Time (25μs/Div)
Time (25μs/Div)
DS8058-05 April 2011www.richtek.com
6
RT8058
V
OUT
(50mV/Div)
I
OUT
(1A/Div)
V
OUT
(50mV/Div)
Load Transient Response
V
= 3.3V, V
IN
OUT
= 1.2V, I
OUT
Time (25μs/Div)
Load Transient Response
V
= 5V, V
IN
OUT
= 1.2V, I
OUT
= 0.5A to 1.5A
= 0A to 1A
V
OUT
(50mV/Div)
I
OUT
(1A/Div)
V
OUT
(50mV/Div)
Load Transient Response
V
= 3.3V, V
IN
OUT
= 1.2V, I
OUT
Time (25μs/Div)
Load Transient Response
V
= 5V, V
IN
OUT
= 1.2V, I
= 0A to 2A
OUT
= 1A to 2A
I
OUT
(1A/Div)
V
OUT
(50mV/Div)
I
OUT
(1A/Div)
Time (25μs/Div)
Load Transient Response
V
= 5V, V
IN
= 1.2V, I
OUT
Time (25μs/Div)
= 0.5A to 1.5A
OUT
I
OUT
(1A/Div)
V
OUT
(50mV/Div)
I
OUT
(1A/Div)
Time (25μs/Div)
Load Transient Response
V
IN
= 5, V
= 1.2V, I
OUT
Time (25μs/Div)
= 1A to 2A
OUT
DS8058-05 April 2011www.richtek.com
7
RT8058
V
OUT
(5mV/Div)
V
LX
(5V/Div)
I
OUT
(1A/Div)
V
OUT
(5mV/Div)
V
= 3.3V, V
IN
V
IN
Output Ripple Noise
= 1.2V, I
OUT
Time (500ns/Div)
Output Ripple Noise
= 5V, V
OUT
= 1.2V, I
OUT
OUT
= 1.5A
= 1.5A
V
OUT
(5mV/Div)
V
LX
(5V/Div)
I
OUT
(1A/Div)
V
OUT
(5mV/Div)
V
IN
V
IN
Output Ripple Noise
= 3.3V, V
= 1.2V, I
OUT
Time (500ns/Div)
Output Ripple Noise
= 5V, V
OUT
= 1.2V, I
OUT
OUT
= 2A
= 2A
V
LX
(5V/Div)
I
OUT
(1A/Div)
V
EN
(2V/Div)
V
OUT
(1V/Div)
I
OUT
(2A/Div)
V
IN
= 3.3V, V
Time (500ns/Div)
Power On from EN
OUT
= 1.2V, R
LOAD
= 0.6Ω
V
LX
(5V/Div)
I
OUT
(1A/Div)
V
EN
(2V/Div)
V
OUT
(1V/Div)
I
OUT
(2A/Div)
V
IN
= 5V, V
Time (500ns/Div)
Power On from EN
OUT
= 1.2V, R
LOAD
= 0.6Ω
Time (500μs/Div)
Time (500μs/Div)
DS8058-05 April 2011www.richtek.com
8
RT8058
V
IN
(2V/Div)
V
OUT
(1V/Div)
I
IN
(1A/Div)
Soft-Start & Inrush Current
V
= 3.3V, V
IN
= 1.2V, I
OUT
OUT
Time (2.5ms/Div)
= 1.5A
V
IN
(2V/Div)
V
OUT
(1V/Div)
I
IN
(1A/Div)
Soft-Start & Inrush Current
V
= 5V, V
IN
= 1.2V, I
OUT
OUT
Time (2.5ms/Div)
= 1.5A
DS8058-05 April 2011www.richtek.com
9
RT8058
Application Information
Function Description
The RT8058 is a 1MHz 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.
Frequency compensation is done internally. The output
voltages are set by external dividers returned to the FB
pin. The output voltage can be set from 0.8V to 5V.
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, RT8058
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, RT8058 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 :
V
= V
OUT
where V
x (1+ R1/R2)
REF
equals to 0.6V typical.
REF
The resistive divider allows the FB pin to sense a fraction
of the output voltage as shown in Figure 1.
V
OUT
R1
FB
RT8058
GND
R2
Figure 1. Setting the Output Voltage
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 RT8058, 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 RT8058 is designed to operate down to an input supply
voltage of 2.7V. One important consideration at low input
supply voltages is that the R
of the P-Channel and
DS(ON)
N-Channel power switches increases. The user should
calculate the power dissipation when the RT8058 is used
at 100% duty cycle with low input voltages to ensure that
thermal limits are not exceeded.
10
DS8058-05 April 2011www.richtek.com
RT8058
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 RT8058 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.
ΔI
V
⎤
⎡
=
L
⎥
⎢
×
Lf
⎦
⎣
V
⎡
−×
1
⎢
⎣
⎤
OUTOUT
⎥
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 :
L(MAX)
⎤
⎡
V
−×
1
⎥
⎢
V
⎦
IN(MAX)
⎣
OUT
⎤
⎥
⎦
⎡
V
=
L
OUT
⎢
Δ×
If
⎣
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,
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
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 1.300 1.750 0.051 0.069
E 2.950 3.050 0.116 0.120
E2 1.300 1.750 0.051 0.069
e 0.500 0.020
L 0.350 0.450
Richtek Technology Corporation
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
0.014 0.018
W-Type 16L QFN 3x3 Package
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 95, Minchiuan Road, Hsintien City
Taipei County, Taiwan, R.O.C.
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.
DS8058-05 April 2011www.richtek.com
15
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