RP506K Series
2 A PWM/VFM Step-down DC/DC Converter with Synchronous Rectifier
NO.EA-296-160523
OUTLINE
The RP506K is a low supply current CMOS-based PWM/VFM step-down DC/DC converter with synchronous
rectifier featuring 2 A
(1)
output current. Internally, a single converter consists of an oscillator, a reference voltage
unit, an error amplifier, a switching control circuit, a mode control circuit, a soft start circuit, a latch type
protection circuit, an under-voltage lockout (UVLO) circuit, a thermal shutdown circuit, and switching transistors.
The RP506K is employing synchronous rectification for improving the efficiency of rectification by replacing
diodes with built-in switching transistors. Using synchronous rectification not only increases circuit performance
but also allows a design to reduce parts count.
Power controlling method can be selected from forced PWM control type or PWM/VFM auto switching control
type by inputting a signal to the MODE pin. In low output current, forced PWM control switches at fixed
frequency rate in order to reduce noise. Likewise, in low output current, PWM/VFM auto switching control
automatically switches from PWM mode to VFM mode in order to achieve high efficiency.
Output voltage type can be selected from an internally fixed output voltage type (RP506Kxx1A/B/D/E) or an
externally adjustable output voltage type (RP506K001C/F). The output voltage of the RP506Kxx1A/B/D/E can
be set by 0.1 V step and the output voltage accuracy is as high as ±1.5% or
±18
mV. The output voltage of the
RP506K001C/F can be set by using the external resistors.
Oscillator frequency can be selected from 2.25 MHz (RP506Kxx1A/B/C) or 1.2 MHz (RP506Kxx1D/E/F). Soft-
start time is Typ. 0.15 ms, and by connecting an external capacitor to the TSS pin, soft-start time is adjustable.
Power good (PG) function monitors the V
OUT
pin voltage or the feedback pin voltage (V
FB
), and switches the
PG pin to low if any abnormal condition is detected.
Protection circuits included in the RP506K are over current protection circuit, latch type protection circuit and
thermal shutdown circuit. Over current protection circuit supervises the inductor peak current in each switching
cycle, and if the current exceeds the L
X
current limit (I
LXLIM
), it turns off Pch Tr. Latch type protection circuit
latches the built-in driver to the OFF state and stops the operation of the step-down DC/DC converter if the
over current status continues or V
OUT
continues being the half of the setting voltage for equal or longer than
protection delay time (tprot). Thermal shutdown circuit detects overheating of the converter if the output pin is
shorted to the ground pin (GND) etc. and stops the converter operation to protect it from damage if the junction
temperature exceeds the specified temperature.
The RP506K is available in DFN(PLP)2527-10 which achieves high-density mounting on boards.
(1)
This is an approximate value. The output current is dependent on conditions and external components.
1
RP506K
NO.EA-296-160523
FEATURES
Supply Current········································ Typ. 48 µA (VFM mode, Lx at no load)
Standby Current ······································ Typ. 0 µA
Input Voltage Range ································ 2.5 V to 5.5 V (Absolute Maximum Ratings: 6.5 V)
Output Voltage Range
(1)
··················
Fixed output voltage type (RP506Kxx1A/B/D/E) : to 3.3 V by 0.1 V step
Adjustable output voltage type (RP506K001C/F) : to 4.0 V
Version
RP506Kxx1A/B
RP506K001C
RP506Kxx1D/E
RP506K001F
Forced PWM Control
PWM/VFM Auto Switching Control
1.1 V to 3.3 V
1.1 V to 4.0 V
0.8 V to 3.3 V
0.8 V to 4.0 V
0.6 V to 3.3 V
0.6 V to 4.0 V
Output Voltage Accuracy ··························· ±1.5% (V
SET(2)
≥ 1.2 V),
··························· ±18 mV (V
SET
< 1.2 V) (RP506Kxx1A/B/D/E)
Feedback Voltage Accuracy ······················· ±9 mV (V
FB
= 0.6 V) (RP506K001C/F)
Output Voltage/Feedback Voltage
Temperature Coefficient ···························· ±100 ppm/ºC
Oscillator Frequency ································ Typ. 2.25 MHz (RP506Kxx1A/B/C)
································· Typ. 1.2 MHz (RP506Kxx1D/E/F)
Oscillator Maximum Duty ·························· Min. 100%
Built-in Driver ON Resistance ····················· Typ. Pch. 0.130 Ω, Nch. 0.125 Ω (V
IN
= 3.6 V)
UVLO Detector Threshold ························· Typ. 2.2 V
Inductor Current Limit Circuit······················ Current limit Typ. 2.8 A
Latch Type Protection Circuit ····················· Typ. 1.5 ms
Package ················································ DFN(PLP)2527−10
APPLICATION
Power source for Li-ion battery-used equipment
Power source for portable communication equipment, camcorder, DSC, Notebook PC
Power source for HDD, WLAN
(1)
(2)
Refer to
Selection Guide
for detailed information.
V
SET
= Set Output Voltage
2
RP506K
NO.EA-296-160523
SELECTION GUIDE
The set output voltage, the output voltage type, the auto-discharge function
(1)
, and the oscillator frequency for
the ICs are user-selectable options.
Selection Guide
Product Name
RP506Kxx1$(y)-TR
Package
DFN(PLP)2527−10
Quantity per Reel
5,000 pcs
Pb Free
Yes
Halogen Free
Yes
xx: Designation of the set output voltage (V
SET
)
(2)
For Fixed Output Voltage Type
(3)
: 0.6 V to 3.3 V in 0.1 V steps
For Adjustable Output Voltage Type: 00 only
(y): If V
SET
includes the 3rd digit, indicate the digit of 0.01 V.
(1.25 V)
Ex. If V
SET
is 1.25 V, RP506K121$5-TR.
$: Designation of Version
Version
RP506Kxx1A
RP506Kxx1B
RP506K001C
RP506Kxx1D
RP506Kxx1E
RP506K001F
Output Voltage Auto-discharge
Type
Function
Fixed
Adjustable
Fixed
Adjustable
No
Yes
No
Yes
No
1.2 MHz
2.25 MHz
V
SET
Oscillator
PWM/VFM
Frequency Forced PWM
Auto Switching
1.1 V to 3.3 V
1.1 V to 4.0 V
0.8 V to 3.3 V
0.8 V to 4.0 V
0.6 V to 3.3 V
0.6 V to 4.0 V
(1)
Auto-discharge function quickly lowers the output voltage to 0 V, when the chip enable signal is switched from the
active mode to the standby mode, by releasing the electrical charge accumulated in the external capacitor.
(2)
V
SET
can be set only within the specified range of voltage. Refer to
Designation of Version
for detailed information.
(3)
0.05 V step is also available as a custom code.
3
RP506K
NO.EA-296-160523
BLOCK DIAGRAM
PV
IN
Ramp
Compensation
Current
Feedback
AV
IN
UVLO
Thermal
Protection
Current
Detector
Switching
Control
L
X
Soft Start
Vref
TSS
(“L” during
Soft Start)
Mode
Control
OSC
PGND
V
OUT
MODE
CE
AGND
Chip
Enable
Over /Under
Voltage
Detection
OVD
UVD
PG
RP506Kxx1A/D Block Diagram
PV
IN
Ramp
Compensation
Current
Feedback
AV
IN
UVLO
Thermal
Protection
Current
Detector
Switching
Control
L
X
Soft Start
Vref
TSS
(“L” during
Soft Start)
Mode
Control
OSC
PGND
V
OUT
MODE
CE
AGND
Chip
Enable
Over /Under
Voltage
Detection
OVD
UVD
PG
RP506Kxx1B/E Block Diagram
4
RP506K
NO.EA-296-160523
PV
IN
Ramp
Compensation
Current
Feedback
AV
IN
UVLO
Thermal
Protection
Current
Detector
Switching
Control
L
X
Soft Start
Vref
TSS
(“L” during
Soft Start)
Mode
Control
OSC
PGND
V
FB
MODE
CE
AGND
Chip
Enable
Over /Under
Voltage
Detection
OVD
UVD
PG
RP506K001C/F Block Diagram
5
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