RP506K Series
2A
*1
PWM/VFM Step-down DC/ DC Converter with Synchronous Rectifier
NO.EA-296-130213
OUTLINE
The RP506K Series are low supply current CMOS-based PWM/VFM step-down DC/DC converters with
synchronous rectifier featuring 2A
*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 0.1V step and the output voltage accuracy is as high as ±1.5% or
±18mV.
The output voltage of the
RP506K001C/F can be set by using the external resistors.
Oscillator frequency can be selected from 2.25MHz (RP506Kxx1A/B/C) or 1.2MHz (RP506Kxx1D/E/F).
Soft-start time is Typ. 0.15ms, and by connecting an external capacitor to the T
SS
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 depends on conditions and external components.
1
RP506K
FEATURES
●
Supply Current ············································· Typ. 48µA (VFM mode, Lx at no load)
●
Standby Current ··········································· Max. 5µA
●
Input Voltage Range····································· 2.5V to 5.5V (Absolute Maximum Ratings: 6.5V)
●
Output Voltage Range
*2
Version
RP506Kxx1A/B
RP506K001C
RP506Kxx1D/E
RP506K001F
Forced PWM control PWM/VFM auto switching control
1.1V to 3.3V
0.8V to 3.3V
1.1V to 3.8V
0.8V to 3.8V
0.6V to 3.3V
0.6V to 3.8V
●
Output Voltage Accuracy······························ ±1.5% (V
SET*3
≥1.2V),
±18mV (V
SET
<1.2V) (RP506Kxx1A/B/D/E)
●
Feedback Voltage Accuracy························· ±9mV(V
FB
=0.6V) (RP506K001C/F)
●
Output Voltage/Feedback Voltage
Temperature Coefficient······························· ±100ppm/ ºC
●
Oscillator Frequency ···································· Typ. 2.25MHz (RP506Kxx1A/B/C)
Typ. 1.2MHz (RP506Kxx1D/E/F)
●
Oscillator Maximum Duty ····························· Min. 100%
●
Built-in Driver ON Resistance ······················ Typ. Pch. 0.130Ω, Nch. 0.125Ω (V
IN
=3.6V)
●
UVLO Detector Threshold···························· Typ. 2.2V
●
Inductor Current Limit Circuit ······················· Current limit Typ. 2.8A
●
Latch Type Protection Circuit ······················· Typ. 1.5ms
●
Package ······················································· DFN(PLP)2527−10
*2
Refer to
Selection Guide
for detailed information. Fixed output voltage type (RP506Kxx1A/B/D/E) can be set by 0.1 V
step.
*3
V
SET
=Set Output Voltage
APPLICATION
●
Power source for Li-ion battery-used equipment
●
Power source for portable communication equipment, camcorder, DSC, Notebook PC
●
Power source for HDD, WLAN
2
RP506K
BLOCK DIAGRAM
PV
IN
Ramp
Compensation
Current
Feedback
AV
IN
UVLO
Thermal
Protection
Current
Detector
Switching
Control
L
X
Soft Start
Vref
T
SS
(“L” during
Soft Start)
Mode
Control
OSC
PGND
V
OUT
MODE
Chip
Enable
CE
AGND
Over /Under
Voltage
Detection
OVD
UVD
PG
Figure 1. RP506Kxx1A/D
PV
IN
Ramp
Compensation
Current
Feedback
AV
IN
UVLO
Thermal
Protection
Current
Detector
Switching
Control
L
X
Soft Start
Vref
T
SS
(“L” during
Soft Start)
Mode
Control
OSC
PGND
V
OUT
MODE
Chip
Enable
CE
AGND
Over /Under
Voltage
Detection
OVD
UVD
PG
Figure 2. RP506Kxx1B/E
3
RP506K
PV
IN
Ramp
Compensation
Current
Feedback
AV
IN
UVLO
Thermal
Protection
Current
Detector
Switching
Control
L
X
Soft Start
Vref
T
SS
(“L” during
Soft Start)
Mode
Control
OSC
PGND
V
FB
MODE
Chip
Enable
CE
AGND
Over /Under
Voltage
Detection
OVD
UVD
PG
Figure 3. RP506K001C/F
4
RP506K
SELECTION GUIDE
The set output voltage, the output voltage type, the auto-discharge function
*4
, and the oscillator frequency
for the ICs are user-selectable options.
Product Name
Package
Quantity per Reel
5,000 pcs
Pb Free
Yes
Halogen Free
Yes
RP506Kxx1$(y)-TR DFN(PLP)2527−10
xx: Designation of the set output voltage (V
SET
)
For Fixed Output Voltage Type: 0.6V (06)
*5
to 3.3V (33) in 0.1V steps
*6
For Adjustable Output Voltage Type: 001 only
(y): If V
SET
includes the 3rd digit, indicate the digit of 0.01V.
(1.25V)
Ex. If V
SET
is 1.25V, RP506K121$5-TR-FE.
$: Designation of version
Version
RP506Kxx1A
RP506Kxx1B
RP506K001C
RP506Kxx1D
RP506Kxx1E
RP506K001F
*4
Output Voltage Auto-discharge
Function
Type
Fixed
Adjustable
Fixed
Adjustable
No
Yes
No
Yes
No
V
SET
Oscillator
PWM/VFM
Frequency Forced PWM
auto switching
2.25MHz
1.1V to 3.3V
1.1V to 3.8V
1.2MHz
0.8V to 3.3V
0.8V to 3.8V
0.6V to 3.3V
0.6V to 3.8V
Auto-discharge function quickly lowers the output voltage to 0V, 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.
*5
V
SET
can be set only within the specified range of voltage. Refer to
Designation of version
for detailed information.
*6
0.05V step is also available as a custom code.
5
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