RP505K Series
1A Step-down DC/DC Converters with Synchronous Rectifier
NO.EA-273-150317
OUTLINE
The RP505K Series are low supply current CMOS-based 1A
*1
step-down DC/DC Converters with synchronous
rectifier. Each of these ICs 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 lock out (UVLO)
circuit, a thermal shutdown circuit, and a switching transistors. A low ripple, high efficiency synchronous rectifier
step-down DC/DC converter can be easily composed of this IC with only an inductor and capacitors. Since the
package is DFN(PLP)2020-8, high density mounting on boards is possible.
In the RP505K series, as for the A version and B version, since feedback resistors are built-in, the voltage is
fixed internally. 0.1V step output can be set by laser-trim and
±1.5%(V
OUT
≥1.2V)
or 18mV(V
OUT
<1.2V) tolerance
is guaranteed. As for the C version, output voltage is adjustable with external divider resisters.
By inputting a signal to MODE pin, the RP505K Series can choose PWM/VFM alternative mode or forced PWM
mode. In low output current, PWM/VFM alternative mode automatically switches from PWM to VFM in order to
achieve high efficiency. Likewise, in low output current, Forced PWM mode switches at fixed frequency in order
to reduce noise.
As protection circuits, the RP505K Series contain a current limit circuit which limits the Lx peak current in each
clock cycle, and a latch type protection circuit which latches the built-in driver to the OFF state if the load current
exceeds the limit value or the output short continues for a specified time (the protection delay time). The latch
protective circuit can be released by once putting the IC into the standby mode with the CE pin and then into the
active mode, or, by turning the power off and back on. Setting the supply voltage lower than the UVLO detector
threshold can also release the latch protective circuit. The RP505K Series also contain a thermal shutdown circuit
which detects the overheating and resets the IC when the junction temperature of the RP505K Series exceeds
the specified temperature.
*1
This is an approximate value, because output current depends on conditions and external parts.
FEATURES
•
•
•
•
Supply Current ...................................................... Typ. 40µA (VFM mode with no-load)
Standby Current .................................................... Max. 5µA
Input Voltage Range ............................................. 2.3V to 5.5V (Absolute maximum rating: 6.5V)
Output Voltage Range (Ver.A,B) ........................... 0.6V to 3.3V (Adjustable in 0.1V steps.
Note: As for 0.8V or less, input voltage range is limited.)
(Ver.C) .............................. 0.8V to 3.3V
Output Voltage Accuracy (Ver.A,B) .......................
±1.5%
(V
OUT
≥1.2V), ±18mV
(V
OUT
<1.2V)
Feedback Voltage Accuracy (Ver.C) .....................
±9mV
(V
FB
=0.6V)
Temperature-Drift Coefficient of Output Voltage/ Feedback
.............................................................................. Typ.
±100ppm/°C
Oscillator Frequency ............................................. Typ. 2.25MHz
Oscillator Maximum Duty Cycle ............................ Min. 100%
Built-in Driver ON Resistance ............................... Typ. Pch. 0.23Ω, Nch. 0.20Ω (V
IN
=3.6V)
UVLO Detector Threshold..................................... Typ. 2.0V
Soft-start Time ....................................................... Typ. 0.15ms
L
X
Current Limit Circuit .......................................... Typ. 1.7A
Latch Type Protection Circuit ................................ Typ. 1.5ms
Package ................................................................ DFN(PLP)2020-8
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•
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•
•
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1
RP505K
SELECTION GUIDE
In the RP505K Series, output voltage, and auto discharge function for the IC are selectable at the user’s request.
Product Name
RP505Kxx1$-TR
Package
DFN(PLP)2020-8
Quantity per Reel
5,000pcs
Pb Free
Yes
Halogen Free
Yes
xx : The output voltage can be designated in the range from 0.6V(06) to 3.3V(33) in 0.1V
*1
steps.
The output voltage adjustable type: xx=00
(For other voltages, please refer to MARK INFORMATIONS.)
$ : Designation of Mask Option
A) Fixed output voltage type, without auto-discharge function at off state
B) Fixed output voltage type, with auto-discharge function at off state
C) Adjustable output voltage type, without auto-discharge function at off state
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.
*1
0.05V step is also available as a custom code.
PIN CONFIGURATIONS
•
DFN(PLP)2020-8
Top View
8
7
6
5
5
Bottom View
6
7
8
∗
1
2
3
4
4
3
2
1
4
RP505K
PIN DESCRIPTIONS
•
RP505K: DFN(PLP)2020-8
Pin No.
1
2
3
4
5
6
7
8
Symbol
MODE
CE
AV
IN
PV
IN
L
X
PGND
AGND
V
OUT
/V
FB
Description
Mode Control Pin (“H” Forced PWM Mode, “L” PWM/VFM Alternative Mode)
Chip Enable Pin ("H" Active)
Input Pin
*1
Input Pin
*1
L
X
Switching Pin
Ground Pin
*1
Ground Pin
*1
Output Pin / Feedback Pin
Tab is GND level. (They are connected to the reverse side of this IC.) The tab is better to be connected to the GND, but
leaving it open is also acceptable.
*1
No.3 pin and No.4 pin, and also No.6 pin and No.7 pin must be wired each other when mounted on boards.
ABSOLUTE MAXIMUM RATINGS
(AGND=PGND=0V)
Symbol
A/PV
IN
V
LX
V
CE
V
OUT
/V
FB
V
MODE
I
LX
P
D
T
a
T
stg
*1
Item
AV
IN
/PV
IN
Input Voltage
L
X
Pin Voltage
CE Pin Input Voltage
V
OUT
/V
FB
Pin Voltage
MODE Pin Voltage
L
X
Pin Output Current
Power Dissipation (Standard Test Land Pattern)*
1
Operating Temperature Range
Storage Temperature Range
Rating
-0.3 to 6.5
-0.3 to A/PV
IN
+ 0.3
-0.3 to 6.5
-0.3 to 6.5
−0.3 to 6.5
1.7
880
-40 to 85
-55 to 125
Unit
V
V
V
V
V
A
mW
°C
°C
For Power Dissipation and Standard Test Land Pattern, please refer to PACKAGE INFORMATION.
ABSOLUTE MAXIMUM RATINGS
Electronic and mechanical stress momentarily exceeded absolute maximum ratings may cause the permanent damages
and may degrade the life time and safety for both device and system using the device in the field. The functional
operation at or over these absolute maximum ratings is not assured.
RECOMMENDED OPERATING CONDITIONS
(ELECTRICAL CHARACTERISTICS)
All of electronic equipment should be designed that the mounted semiconductor devices operate within the
recommended operating conditions. The semiconductor devices cannot operate normally over the recommended
operating conditions, even if when they are used over such conditions by momentary electronic noise or surge. And the
semiconductor devices may receive serious damage when they continue to operate over the recommended operating
conditions.
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