RP505K Series
1A
∗
PWM/VFM Step-down DC/DC Converter with Synchronous Rectifier
The RP505K Series are low supply current CMOS-based PWM/VFM step-down DC/DC converters with synchronous rectifier. RP505K can be
selected from two control types by input signal to the MODE pin - forced PWM control or PWM/VFM auto switching control in which mode
automatically switches to high-efficiency VFM mode in low output current. The xx1A/B version with an internally fixed output voltage type
and the 001C version with an externally adjustable output voltage type are available. RP505K includes a soft start circuit, an under-voltage
lockout circuit (UVLO), thermal shutdown circuit and a latch protection circuit. By simply using an inductor, (resistors) and capacitors as
external components, a high-efficiency step-down DC/DC converter can be easily configured. The small inductor (2.2μH) and output
capacitor (10μF) can be used by the switching of 2.25MHz. A 2mm square compact DFN(PLP)2020-8 package is available.
FEATURES
•
Supply Current (I
DD1
)·················· Typ. 500μA (Switching)
•
Supply Current (I
DD2
)·················· Typ. 40μA (No switching, VFM)
•
Supply Current (I
DD2
)·················· Typ. 500μA (No switching, PWM)
•
Standby Current (I
standby
) ············ Max. 5μA (CE="L")
•
Input Voltage Range (V
IN
) ·········· 2.3V to 5.5V (V
SET
≥
0.8V)
•
Output Voltage Range (V
OUT
)····· 0.6V to 3.3V
∗∗
(Internally fixed, RP505Kxx1A/B)
•
•
•
•
Oscillator Maximum Duty Cycle (Maxduty)···· Min. 100%
•
UVLO Detect Voltage (V
UVLO
) ·············· Typ. 2.0V
•
Soft Start Time (t
start
) ···························· Typ. 0.15ms
•
Thermal Shutdown Circuit ··················· Stops at 140°C.
•
Coil-current Limit Circuit ···················· Current limit Typ. 1.7A
•
Latch Protection Circuit ······················· Delay time for protection
•
Auto-discharge Function······················ B Version
•
MODE Pin ·········································· "H": forced PWM control,
•
Package··············································· DFN(PLP)2020-8
Typ. 1.5ms
"L": PWM/VFM auto switching control
0.8V to 3.3V (Externally djustable, RP505K001C)
(Feedback Voltage : 0.6V)
Output Voltage Accuracy ···········
±
1.5% (Feedback Voltage Accuracy :
±
9mV)
Output Current (I
OUT
)·················· 1A
∗
Oscillator Frequency (f
osc
)·········· 2.25MHz
∗)
This is an approximate value, because output current depends on conditions and external parts.
∗∗)
For less than 0.8V, the input voltage range is limited. For details, please refer to the datasheet.
BLOCK DIAGRAMS
RP505Kxx1A/B
(Internally fixed output voltage type)
PV
IN
Ramp
Compensation
Current
Feedback
Ramp
Compensation
Current
Feedback
RP505K001C
(Externally adjustable output voltage type)
PV
IN
AV
IN
UVLO
Thermal
Shutdown
Current
Detector
Switching
Control
L
X
AV
IN
UVLO
Thermal
Shutdown
Current
Detector
Switching
Control
L
X
Soft Start
Vref
Soft Start
Vref
MODE
CE
Chip
Enable
Mode
Control
OSC
PGND
MODE
CE
Chip
Enable
Mode
Control
OSC
PGND
V
OUT
V
FB
AGND
AGND
SELECTION GUIDES
Halogen Free
Part No.
RP505K.xx.1.
∗
-TR
DFN(PLP)2020-8 5,000 pcs
RP505K.00.1.$.-TR
Package
Q'ty per Reel
V
IN
TYPICAL APPLICATIONS
RP505Kxx1A/B
L
PV
IN
L
X
2.2μH
C
OUT
10μF
C
IN
4.7μF
V
OUT
V
IN
RP505K001C
L
PV
IN
L
X
2.2μH
R
1
C
1
C
OUT
10μF
V
OUT
.xx.
: Specify the output voltage within the range of
0.6V (.06.) to 3.3V (.33.) in 0.1V steps.
(For externally adjustable output voltage type (.00.))
.∗
: Select from (.A.) internally fixed output voltage type,
without auto-discharge function or
(.B.) internally fixed output voltage type, with auto-discharge function.
.$.
: (.C.) externally adjustable output voltage type,
without auto-discharge function
C
IN
4.7μF
AV
IN
V
OUT
AV
IN
V
FB
R
2
CE
MODE
AGND
CE
MODE
AGND
PGND
PGND
L : MIPSA2520D2R2 (FDK)
C
IN
: C1608JB0J475K (TDK)
C
OUT
: C1608JB0J106M (TDK)
Set Output Voltage
0.6V
≤
V
SET
< 1.6V
1.6V
≤
V
SET
≤
2.3V
2.3V < V
SET
≤
3.3V
Inductor
1.0μH or more
1.5μH or more
2.2μH or more
PACKAGE
DFN(PLP)2020-8
Top View
8
7
6
5
TYPICAL CHARACTERISTIC
RP505K331x
8
∗
Efficiency vs. Output Current
Bottom View
5
6
7
1
2
3
4
4
3
2
1
1
2
3
4
MODE
CE
AV
IN
∗∗
PV
IN
∗∗
5
6
7
8
L
X
PGND
∗∗
AGND
∗∗
V
OUT
or V
FB
∗
) The tab is substrate level (GND).
∗∗
) No.3 pin and No.4 pin, No.6 pin and No.7 pin must be wired together when it is mounted on board.
100
90
80
70
60
50
40
30
20
10
0
Efficiency
η
(%)
V
IN
=4.3V, PWM/VFM
V
IN
=5.0V, PWM/VFM
V
IN
=4.3V, forced PWM
V
IN
=5.0V, forced PWM
1
APPLICATIONS
•
Power source for battery-powered equipment
•
Power source for Wireless LAN terminals
No.EK-273-121001
10
100
Output Current I
OUT
(mA)
1000
•
Power source for hand-held communication equipment, cameras, and VCRs
Step-down DC/DC Converter
RP505K Series
RP50x Series 1A
Step-down DC/DC Converter Comparison
RP505K Series
Control
Output Current*
Supply Current（PWM Mode）
Supply Current（VFM Mode）
Supply Current（Standby Mode）
Input Voltage Range
Output Voltage Range
Output Voltage Accuracy
Oscillator Frequency
Oscillator Maximum Duty Cycle
UVLO Detect Voltage
Soft-start Time
Latch Protection Circuit
（Protection
Delay Time）
Coil-current Limit Circuit
Inductor
PWM/VFM automatic shift /
Forced PWM
（It
can be switched by MODE pin）
1A
Typ. 500μA
Typ. 40μA
Max. 5μA
2.3V to 5.5V
0.6V to 3.3V**
∗∗)
For less than 0.8V, the input voltage range is limited.
Step-down DC/DC Converter
1A
∗
PWM/VFM Step-down DC/DC Converter with Synchronous Rectifier
RP501K Series
PWM/VFM automatic shift/
Fixed PWM
（It
can be switched by MODE pin）
1A
Typ. 450μA
Typ. 140μA
Max. 5μA
2.5V to 5.5V
1.0V to 3.3V
±1.5%
Typ. 2.25MHz
Min.100%
Typ. 2.2V
Typ. 0.14ms
Typ. 2.0ms
Typ. 1.5A
2.2μH to 4.7μH
Externally adjustable
±1.5%
Typ. 2.25MHz
Min.100%
Typ. 2.0V
Typ. 0.15ms
Typ. 1.5ms
Typ. 1.7A
Output Voltage
Inductor
0.6V
≤
V
OUT
< 1.6V
1.0
μ
H or more
1.6V
≤
V
OUT
≤
2.3V
1.5
μ
H or more
2.3V < V
OUT
≤
3.3V
2.2
μ
H or more
DFN(PLP)2020-8
Built-in Thermal shutdown circuit
A Version
Fixed output voltage type,
Without auto-discharge function
B Version
Fixed output voltage type,
With auto-discharge function
C Version
Adjustable output voltage type,
Without auto-discharge function
Package
Others
DFN(PLP)2527-10
-
A Version
Without auto-discharge function
B Version
With auto-discharge function
Version
*) This is an approximate value, because output current depends on conditions and external parts.
The currently available information as of October 2012 is provided in this New Product News.
EK-273-121001
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