RP504x SERIES
600mA Step-down DC/DC Converter with Synchronous Rectifier
NO.EA-259-130520
1
OUTLINE
The RP504x Series are low supply current CMOS-based 600mA 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(Ver.A, D), a soft-start circuit, a "latch type" protection circuit, an
under voltage lockout (UVLO) circuit, and 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
packages are SOT-23-5, DFN1616-6B, DFN(PLP)1216-6F, high density mounting on boards is possible.
As protection circuits, the RP504x 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.
In terms of the output voltage, since the feedback resistances are built-in, the voltage is fixed internally. 0.1V
step output can be set by laser-trim and 1.5% or 18mV tolerance depending on the output voltage is
guaranteed. By inputting a signal to a MODE pin, the RP504x Series can be switched between PWM/VFM auto
switching control and Forced PWM control. PWM/VFM auto switching control switches to high-efficiency VFM
mode in low output current. Forced PWM control switches to fixed-frequency Forced PWM mode for reducing
noise in low output current.
)This is an approximate value, because output current depends on conditions and external parts.
FEATURES
Supply Current ...................................................... Typ. 25A(at VFM mode, at no load)
Standby Current .................................................... Max. 5A
Input Voltage Range ............................................. 2.3V to 5.5V (VOUT≧1.0V)
Output Voltage Range........................................... 0.8V to 3.3V (With a 0.1V step)
Output Voltage Accuracy....................................... 1.5% (VOUT1.2V), 18mV (VOUT<1.2V)
Temperature-Drift Coefficient of Output Voltage ... Typ. 40ppm/C
Oscillator
Frequency ............................................. Typ. 2.25MHz
Oscillator Maximum Duty Cycle............................ Min. 100%
Built-in Driver ON Resistance ............................... Typ. Pch. 0.34、Nch. 0.43(VIN=3.6V)
UVLO Detector Threshold..................................... Typ. 2.0V
Soft Start Time....................................................... Typ. 0.15ms
L
X Current Limit ..................................................... Typ. 900mA
Latch type Protection Circuit................................. Typ. 1.5ms
Auto discharge function ........................................ Only for D Version
Two choices of Switching Mode............................ DFN1616-6B and DFN(PLP)1216-6F are available in
adjustable switching control options from PWM/VFM auto switching type or Forced PWM type by using
MODE pin. SOT-23-5 is available in fixed switching control options: PWM/VFM auto switching type for B
version or Forced PWM type for C version.
Packages .............................................................. SOT-23-5, DFN1616-6B, DFN(PLP)1216-6F
RP504x
2
APPLICATIONS
Power source for battery-powered equipment.
Power source for hand-held communication equipment, cameras, VCRs, camcorders.
Power source for HDD, portable equipment.
BLOCK DIAGRAMS
RP504xxxxA
RP504xxxxB
SWITCHING
CONTROL
CURRENT
PROTECTION
SOFT
START
VREF
Lx
VOUT
VIN
CE
GND
OSCILLATOR
PWM
CURRENT
FEEDBACK
RAMP
COMPENSATION
UVLO
MODE
CHIP
ENABLE
SWITCHING
CONTROL
CURRENT
PROTECTION
SOFT
START
VREF
OSCILLATOR
PWM
CURRENT
FEEDBACK
RAMP
COMPENSATION
UVLO
MODE
CHIP
ENABLE
VIN
CE
Lx
VOUT
GND
RP504x
3
RP504xxxxC
RP504xxxxD
SWITCHING
CONTROL
CURRENT
PROTECTION
SOFT
START
VREF
Lx
VOUT
VIN
CE
GND
OSCILLATOR
CURRENT
FEEDBACK
RAMP
PWM
COMPENSATION
UVLO
MODE
CHIP
ENABLE
SWITCHING
CONTROL
CURRENT
PROTECTION
SOFT
START
VREF
LX
VIN
VOUT
CE
GND
OSCILLATOR
PWM
CURRENT
FEEDBACK
RAMP
COMPENSATION
CHIP
ENABLE
UVLO
MODE
RP504x
4
SELECTION GUIDE
In the RP504x Series, output voltage, MODE control, auto discharge function, and package for the ICs are
selectable at the user’s request.
Product Name Package Quantity per Reel Pb Free Halogen Free
RP504Nxx1$-TR-FE SOT-23-5 3,000 pcs Yes Yes
RP504Lxx1$-TR DFN1616-6B 5,000 pcs Yes Yes
RP504Kxx1$-E2 DFN(PLP)1216-6F 5,000 pcs Yes Yes
xx :
$ :
The output voltage can be designated in the range from 0.8V(08) to 3.3V(33) in 0.1V steps1.
Designation is possible in the range from 0.8V to 3.3V with a step of 0.1V
(Refer to the marking information)
Designation of mask option
Symbol Package Mode Control Auto discharge function
A DFN1616-6B
DFN(PLP)1216-6F
Yes
(“H” forced PWM,
“L” PWM/VFM automatic shift)
No
B SOT-23-5 No
(PWM/VFM automatic shift) No
C SOT-23-5 No
(forced PWM) No
D DFN1616-6B
DFN(PLP)1216-6F
Yes
(“H” forced PWM,
“L” PWM/VFM automatic shift)
Yes
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
SOT-23-5 DFN1616-6B DFN(PLP)1 216-6F
Top View
1
4
5
2 3
(mark side)
Top View
3
4
2
5
1
6
Bottom Vi ew
1
6
2
5
3
4
Top View
312
564
Bottom Vi ew
13 2
54 6
RP504x
5
PIN DESCRIPTIONS
RP504Nxx1B, RP504Nxx1C : SOT-23-5
Pin No. Symbol Description
1 VOUT Output Pin
2 GND Ground Pin
3 LX LX Switching Pin
4 VIN Input Pin
5 CE Chip Enable Pin ("H" Active)
RP504Lxx1A, RP504Lxx1D : DFN1616-6B
Pin No. Symbol Description
1 CE Chip Enable Pin ("H" Active)
2 MODE Mode Control Pin (“H” forced PWM, “L” PWM/VFM automatic shift)
3 VIN Input Pin
4 LX LX Switching Pin
5 GND Ground Pin
6 VOUT Output 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.
RP504Kxx1A, RP504Kxx1D : DFN(PLP)1216-6F
Pin No. Symbol Description
1 VIN Input Pin
2 MODE Mode Control Pin (“H” forced PWM, “L” PWM/VFM automatic shift)
3 CE Chip Enable Pin ("H" Active)
4 VOUT Output Pin
5 GND Ground Pin
6 LX LX Switching Pin
RP504x
6
ABSOLUTE MAXIMUM RATINGS
(GND=0V)
Symbol Item Rating Unit
VIN VIN Input Voltage -0.3 to 6.5 V
VLX LX Pin Voltage -0.3 to VIN + 0.3 V
VCE CE Pin Input Voltage -0.3 to 6.5 V
VMODE Mode Control Pin Voltage -0.3 to 6.5 V
VOUT VOUT Pin Voltage -0.3 to 6.5 V
ILX LX Pin Output Current 900 mA
Power Dissipation (SOT-23-5) 420
Power Dissipation (DFN1616-6B) 640
PD
Power Dissipation (DFN(PLP)1216-6F) 385
mW
Ta Operating Temperature Range -40 to 85 C
Tstg Storage Temperature Range -55 to 125 C
) For Power Dissipation, 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.
RP504x
7
ELECTRICAL CHARACTERISTICS
RP504xxxxA, RP504xxxxD (Ta=25C)
Symbol Item Conditions Min. Typ. Max. Unit
VOUT 1.0 2.3 5.5
VIN Operating Input Voltage VOUT <1.0 2.3 4.5
V
VOUT1.2V 0.985 1.015
VOUT Output Voltage VIN=VCE=3.6V
or VSET+1V VOUT<1.2V -0.018 +0.018 V
VOUT/T Output Voltage Temperature
Coefficient -40C
Ta
85C ±40
ppm/C
fosc Oscillator Frequency VIN=VCE=3.6V or VSET+1V 1.95 2.25 2.55 MHz
IDD1 Supply Current 1 VIN=VCE=5.5V, VOUT=VSET0.8 400 800
A
VMODE=0V 25 40
IDD2 Supply Current 2 VIN=VCE=VOUT=5.5V
VMODE=5.5V 400 800 A
Istandby Standby Current VIN=5.5V,VCE=0V 0 5
A
ICEH CE "H" Input Voltage VIN=VCE=5.5V -1 0 1
A
ICEL CE "L" Input Voltage VIN=5.5V,VCE=0V -1 0 1
A
IMODEH Mode "H" Input Current VIN=VMODE=5.5V -1 0 1
A
IMODEL Mode "L" Input Current VIN=5.5V, VMODE=0V -1 0 1
A
IVOUTH VOUT "H" Input Current1 VIN=VOUT=5.5V,VCE=0V -1 0 1
A
IVOUTL VOUT "L" Input Current VIN=5.5V,VCE=VOUT=0V -1 0 1
A
ILXLEAKH LX Leakage Current "H" VIN=VLX=5.5V,VCE=0V -1 0 5
A
ILXLEAKL LX Leakage Current "L" VIN=5.5V,VCE=VLX=0V -5 0 1
A
VCEH CE "H" Input Voltage VIN=5.5V 1.0 V
VCEL CE "L" Input Voltage VIN=2.3V 0.4 V
VMODEH Mode ”H” Input Voltage VIN=VCE=5.5V 1.0 V
VMODEL Mode ”L” Input Voltage VIN=VCE=2.3V 0.4 V
RLOW Nch On Resistance2 VIN=3.6V,VCE=0V 30
RONP On Resistance of Pch Tr. VIN=3.6V, ILX=100mA 0.34
RONN On Resistance of Nch Tr. VIN=3.6V, ILX=100mA 0.43
Maxduty
Oscillator Maximum Duty Cycle
100 %
tstart Soft-start Time VIN=VCE=3.6V or VSET+1V 150 310
s
ILXlim Lx Current Limit VIN=VCE=3.6V or VSET+1V 700 900 mA
tprot Protection Delay Time VIN=VCE=3.6V or VSET+1V 0.5 1.5 5 ms
VUVLO1 UVLO Detector Threshold VIN=VCE 1.9 2.0 2.1 V
VUVLO2 UVLO Released Voltage VIN=VCE 2.0 2.1 2.2 V
Test circuit is "OPEN LOOP" and AGND=PGND=0V unless otherwise specified.
1) without auto discharge version only
2) with auto discharge version only
RP504x
8
RP504xxxxB, RP504xxxxC (Ta=25C)
Symbol Item Conditions Min. Typ. Max. Unit
VOUT 1.0 2.3 5.5
VIN Operating Input Voltage VOUT <1.0 2.3 4.5 V
VOUT
≧
1.2V 0.985 1.015
VOUT Output Voltage VIN=VCE=3.6V
or VSET+1V VOUT < 1.2V -0.018 +0.018 V
VOUT/T Output Voltage Temperature
Coefficient -40C
Ta
85C ±40
ppm/C
fosc Oscillator Frequency VIN=VCE=3.6V or VSET+1V 1.95 2.25 2.55 MHz
IDD1 Supply Current 1 VIN=VCE=5.5V, VOUT=VSET0.8 400 800
A
RP504xxxxB 40 60
IDD2 Supply Current 2 VIN=VCE=VOUT=5.5V RP504xxxxC 500 840 A
Istandby Standby Current VIN=5.5V,VCE=0V 0 5
A
ICEH CE "H" Input Voltage VIN=VCE=5.5V -1 0 1
A
ICEL CE "L" Input Voltage VIN=5.5V,VCE=0V -1 0 1
A
IVOUTH VOUT "H" Input Current VIN=VOUT=5.5V,VCE=0V -1 0 1
A
IVOUTL VOUT "L" Input Current VIN=5.5V,VCE=VOUT=0V -1 0 1
A
ILXLEAKH LX Leakage Current "H" VIN=VLX=5.5V,VCE=0V -1 0 5
A
ILXLEAKL LX Leakage Current "L" VIN=5.5V,VCE=VLX=0V -5 0 1
A
VCEH CE "H" Input Voltage VIN=5.5V 1.0 V
VCEL CE "L" Input Voltage VIN=2.3V 0.4 V
RONP On Resistance of Pch Tr. VIN=3.6V, ILX=100mA 0.34
RONN On Resistance of Nch Tr. VIN=3.6V, ILX=100mA 0.43
Maxduty
Oscillator Maximum Duty Cycle
100 %
tstart Soft-start Time VIN=VCE=3.6V or VSET+1V 150 310
s
ILXlim LX Current Limit VIN=VCE=3.6V or VSET+1V 700 900 mA
tprot Protection Delay Time VIN=VCE=3.6V or VSET+1V 0.5 1.5 5 ms
VUVLO1 UVLO Detector Threshold VIN=VCE 1.9 2.0 2.1 V
VUVLO2 UVLO Released Voltage VIN=VCE 2.0 2.1 2.2 V
Test circuit is "OPEN LOOP" and AGND=PGND=0V unless otherwise specified.
RP504x
9
TYPICAL APPLICATION
RP504N:SOT-23-5 (MODE Pin is not included.)
COU T 4. 7F
CE
VIN LX
VOUT
VIN
CIN 2.2F L 2.2
H
Load
GN D
RP504N
Series
Control
RP504L:DFN1616-6B / RP504K:DFN(PLP)1216-6F (MODE Pin is included.)
COU T 4. 7F
CE
MODE
VIN LX
VOUT
VIN
CIN 2.2F L 2.2
H
Load
GN D
RP504L,K
Series
Control
Control
) MODE=“H” forced PWM
MODE=“L” PWM/VFM automatic shift
Symbol Recommendation components
2.2F C1608JB0J225K (TDK)
2.2F2 C1005JB0J225K (TDK)
JMK105BJ225MV (Taiyo Yuden)
CIN
4.7F
Ceramic
C1005X5R0J475M (TDK)
JMK105BJ475MV (Taiyo Yuden)
COUT 4.7F Ceramic C1608JB0J475K (TDK)
GRM188B30J475KE18 (Murata)
L 2.2H Inductor
MIPSZ2520D2R2 (FDK)
MIPS2520D2R2 (FDK)
MLP2520S2R2M (TDK)
VLS252010T-2R2M (TDK)
RP504x
10
TECHNICAL NOTES
When you use these ICs, consider the following issues:
Set external components such as an inductor, CIN, COUT as close as possible to the IC, in particular, minimize
the wiring to VIN pin and PGND pin. Reinforce the VIN, PGND, and VOUT lines sufficiently. Large switching
current may flow in these lines. If the impedance of VIN and PGND lines is too large, the internal voltage level in
this IC may shift caused by the switching current, and the operation might be unstable. The wiring between
VOUT and load and between L and VOUT should be separated.
The recommended capacitance value for the CIN capacitor connected between the VIN and PGND pins is
2.2µF or more. Also, the recommended capacitance value for the COUT capacitor is 4.7µF ~ 10µF.Please be
aware of the characteristics of bias dependence and temperature fluctuation of ceramic capacitor.
Choose an inductor with inductance range from 2.2H to 4.7H. The phase compensation has been made by
these values with output capacitors. The recommendation characteristics of the inductor are low DC resistance,
large enough permissible current, and strong against the magnetic saturation. Inductance value may shift
depending on an inductor. If the inductance value at an actual load current is low, LX peak current may increase
and may overlap the LX current limit. As a result, over current protection may work.
Over current protection circuit, Latch-type protection circuit may be affected by self-heating and heat radiation
environment.
The performance of power supply circuits using this IC largely depends on the peripheral circuits. Please be
very careful when setting the peripheral parts. When designing the peripheral circuits of each part, PCB
patterns, and this IC, please do not exceed the rated values (Voltage, Current, Power).
RP504x
11
Operation of step-down DC/DC converter and Output Current
The DC/DC converter charges energy in the inductor when LX transistor is ON, and discharges the energy
from the inductor when LX transistor is OFF and controls with less energy loss, so that a lower output voltage
than the input voltage is obtained. The operation will be explained with reference to the following diagrams:
<Basic Circuit> <Current through L>
Pch Tr L
Nch Tr
VIN
i1
VOUT
CL
i2
GND
T=1/fosc
ton toff
topen
ILmin
ILmax
IL
i1 i2
Step 1 : Pch Tr. turns on and current IL (=i1) flows, and energy is charged into CL. At this moment, IL increases
from ILmin (=0) to reach ILmax in proportion to the on-time period (ton) of Pch Tr.
Step 2 : When Pch Tr. turns off, Synchronous rectifier Nch Tr. turns on in order that L maintains IL at ILmax, and
current IL (=i2) flows.
Step 3: IL (=i2) decreases gradually and reaches IL=ILmin=0 after a time period of topen, and Nch Tr. turns off.
Provided that in the continuous mode, next cycle starts before IL becomes to 0 because toff time is not
enough. In this case, IL value increases from this ILmin (>0).
In the case of PWM control system, the output voltage is maintained by controlling the on-time period (ton), with
the oscillator frequency (fosc) being maintained constant.
The maximum value (ILmax) and the minimum value (ILmin) of the current flowing through the inductor are the
same as those when Pch Tr. turns on and off.
The difference between ILmax and ILmin, which is represented by I:
I = ILmax ILmin = VOUT topen / L = (VIN VOUT) ton / L ......................................... Equation 1
wherein,
T = 1 / fosc = ton + toff
duty (%)= ton / T 100 = ton fosc 100
topen toff
In Equation 1, VOUT topen / L and (VIN VOUT) ton / L respectively show the change of the current at "ON", and
the change of the current at "OFF".
RP504x
12
Discontinuous mode and Continuous mode
When the output current (IOUT) is relatively small, topen < toff as illustrated in the above diagram. In this case,
the energy is charged in the inductor during the time period of ton and is discharged in its entirely during the time
period of toff, therefore ILmin becomes to zero (ILmin=0). When IOUT is gradually increased, eventually, topen
becomes to toff (topen=toff), and when IOUT is further increased, ILmin becomes larger than zero (ILmin>0). The
former mode is referred to as the discontinuous mode and the latter mode is referred to as continuous mode.
Discontinuous mode Continuous mode
ILmax
ILmin
ton toff
T=1/fosc
ILmax
ILmin
ton toff
T=1/fosc
IL
topen
IL
Iconst
tt
In the continuous mode, when Equation 1 is solved for ton and assumed that the solution is tonc,
tonc = T VOUT / VIN .......................................................................................................Equation 2
When ton<tonc, the mode is the discontinuous mode, and when ton=tonc, the mode is the continuous mode.
RP504x
13
Output Current and selection of External components
The relation between the output current and external components is as follows:
(Wherein, Ripple Current p-p value is described as IRP, ON resistance of Pch Tr. and Nch Tr. of LX are
respectively described as RONP and RONN, and the DC resistor of the inductor is described as RL.)
When Pch Tr. of LX is ON:
VIN = VOUT + (RONP + RL) IOUT + L IRP / ton ................................................................. Equation 3
When Pch Tr. of LX is "OFF" (Nch Tr. is "ON"):
L IRP / toff = RONN IOUT + VOUT + RL IOUT ................................................................. Equation 4
Put Equation 4 to Equation 3 and solve for ON duty of Pch transistor, DON = ton / (toff + ton),
DON = (VOUT + RONN IOUT + RL IOUT) / (VIN + RONN IOUT RONP IOUT)....................... Equation 5
Ripple Current is as follows:
IRP = (VIN VOUT RONP IOUT RL IOUT) DON / fosc / L............................................. Equation 6
wherein, peak current that flows through L, and LX Tr. is as follows:
ILXmax = IOUT + IRP / 2 .................................................................................................... Equation 7
Consider ILXmax, condition of input and output and select external components.
The above explanation is directed to the calculation in an ideal case in continuous mode.
RP504x
14
TIMING CHART
(1) Soft Start Time
In the case of starting this IC with CE
In the case of starting this IC with CE, the operation can be as in the timing chart below.
When the voltage of CE pin (VCE) is beyond the threshold level, the operation of the IC starts. The threshold
voltage of CE pin is in between CE "H" input voltage (VCEH) and CE "L" input voltage (VCEL) described in the
electrical characteristics table. Soft-start circuit operates, and after the certain time, the reference voltage
inside the IC (VREF) is rising gradually up to the constant value.
VCEH
Soft-start Time
IC Internal Voltage
Reference
VCEL
Threshold Level
Lx Voltage
(VCE)
(VREF) Soft-start Circuit
operating
(
VLX
)
Depending on Power supply,
Load Current, External Components
(VOUT)
Output Voltage
CE Pin
Input Voltage
PWM mode operating
during the Soft-start Time
Soft-start time is the time interval from soft start circuit starting point to the reference voltage level reaching
point up to this constant level.
Soft start time is not always equal to the turn-on speed of DC/DC converter.
The power supply capacity for this IC, load current, inductance and capacitance values affect the turn-on
speed.
In the case of starting with power supply
In the case of starting with power supply, when the input voltage (VIN) is larger than UVLO released voltage
(VUVLO2), soft start circuit operates, and after that, the same explanation above is applied to the operation.
Soft-start time is the time interval from soft start circuit starting point to the reference voltage level reaching
point up to this constant level.
Output Voltage
Input Voltage
VUVLO2
IC Internal Voltage
Reference
VUVLO1
Lx Voltage
Set VOUT
Set VOUT
Soft-start Time
Depending on Power supply,
Load Current, External Components
PWM mode operating during the Soft-start Time
(VOUT)
(VIN)
(VREF)
(VLX)
Turn-on speed is affected by next conditions;
(a) Input Voltage (VIN) rising speed depending on the power supplier to the IC and input capacitor CIN.
(b) Output Capacitor COUT value and load current value.
RP504x
15
(2) Under Voltage Lockout (UVLO) Circuit
The step-down DC/DC converter stops and ON duty becomes 100%, if input voltage (VIN) becomes less
than the set output voltage (Set VOUT), the output voltage (VOUT) gradually drops according to the input
voltage (VIN). If the input voltage drops more and becomes less than UVLO detector threshold (VUVLO1), the
under voltage lockout circuit (UVLO) operates, the IC internal reference voltage (VREF) stops, switching
transistors turn off and the output voltage drops according to the load and output capacitor COUT value.
To restart the normal operation, the input voltage (VIN) must be more than the UVLO released voltage
(VUVLO2).
The timing chart below describes the operation with varying the input voltage (VIN).
VUVLO2
VUVLO1
Set VOUT
Set VOUT
Output Voltage
Input Voltage
IC Internal Voltage
Reference
Lx Voltage
Soft-start Time
Depending on Power supply,
Load Current, External Components
(VOUT)
(VIN)
(VREF)
(VLX)
Actually, the waveform of VOUT at UVLO working and releasing varies depending on the initial voltage of
COUT and load current situation.
RP504x
16
(3) Over Current Protection Circuit, Latch Type Protection Circuit
Over current protection circuit supervises the inductor peak current (the current flowing through Pch
transistor) in each switching cycle, and if the current exceeds the LX current limit (ILXlim), turns off Pch
transistor. The LX current limit of RP504x is Typ.900mA.
Latch type protection circuit latches the built-in driver to the OFF state and stops the operation of DC/DC
converter if the over current status continues or the output voltage continues being the half of the setting
voltage for equal or longer than protection delay time (tprot).
LX current limit (ILXlim) and protection delay time (tprot) could be easily affected by self-heating or ambient
environment. If the input voltage (VIN) drops drastically or becomes unstable due to short-circuit, the
protection operation and protection delay time may be affected.
Protection Delay Time (tprot)
Lx Current Limit (ILXlim)
Lx Current
Pch Tr. Current
Lx Voltage
(VLX)
To release the condition of latch type protection, restart this IC by inputting "L" signal to CE pin, or restart
this IC with power-on or make the supply voltage lower than UVLO detector threshold (VUVLO1) level.
The timing chart shown below describes the changing process of input voltage rising, stable operating,
operating with large current, reset with CE pin, stable operating, input voltage falling, input voltage
recovering, and stable operating.
Point(1) : If the large current flows through the circuit or the IC goes into low output voltage condition due to
short-circuit or other reasons, the latch type protection circuit latches the built-in driver to OFF state after the
protection delay time (tprot). Then, VLX becomes "L" and the output voltage turns OFF. In this timing chart
below, the latch protective circuit can be released by once putting the IC into "L" with the CE pin and then
into "H" again.
Point(2) : The latch type protection can be released by UVLO reset by making the input voltage lower than
the UVLO detector threshold(VUVLO1).
Input Voltage
(VIN)
Set VOUT
UVL
Detect Voltage (VUVLO1)
CE Pin
Input Voltage
(VCE)
Set VOUT
Threshold Level
Lx Voltage
(VLX )
Set VOUT
Output Voltage
(VOUT)
UVL
Release Voltage (VUVLO 2)
(1) (2)
Sof t-start Tim e
Set VOUT
Soft-start Tim e Soft-start Time
Stable
operation
Protection Delay Time Protection Delay Time
UV LO Reset
CE Res et
Latch-type Protection Latch-type Protecti on
Stable
operation
Stable
operation
RP504x
17
TYPICAL CHARACTERISTICS
1) Output Voltage vs. Output Current
RP504x VOUT=0.8V RP504x VOUT=0.8V
MODE=“L”PWM/VFM automatic shift MODE=“H” forced PWM
0.780
0.785
0.790
0.795
0.800
0.805
0.810
0.815
0.820
0.01 0.1 1 10 100
Output Current I
OUT
(mA)
Output Voltage V
OUT
(V)
VIN=3.6V
VIN=4.5V
0.780
0.785
0.790
0.795
0.800
0.805
0.810
0.815
0.820
0 100 200 300 400 500 600
Output Current IOUT (m A)
Output Voltage V OUT (V)
VIN=3 .6 V
VIN=4 .5 V
RP504x VOUT=1.2V RP504x VOUT=1.2V
MODE=“L”PWM/VFM automatic shift MODE=“H” forced PWM
1.180
1.185
1.190
1.195
1.200
1.205
1.210
1.215
1.220
0.01 0.1 1 10 100
Output Current I
OUT
(mA)
Output Voltage V
OUT
(V)
VIN=3.6V
VIN=5.0V
1.180
1.185
1.190
1.195
1.200
1.205
1.210
1.215
1.220
0 100 200 300 400 500 600
Output Current I
OUT
(mA)
Output Voltage V
OUT
(V)
VIN=3.6V
VIN=5.0V
RP504x VOUT=1.8V RP504x VOUT=1.8V
MODE=“L”PWM/VFM automatic shift MODE=“H” forced PWM
1.780
1.790
1.800
1.810
1.820
1.830
0.01 0.1 1 10 100
Output Current I
OUT
(mA)
Output Voltage V
OUT
(V)
VIN=3.6V
VIN=5.0V
1.780
1.790
1.800
1.810
1.820
1.830
0 100 200 300 400 500 600
Output Current I
OUT
(mA)
Output Voltage V
OUT
(V)
VIN=3 .6V
VIN=5 .0V
RP504x
18
RP504x VOUT=3.3V RP504x VOUT=3.3V
MODE=“L”PWM/VFM automatic shift MODE=“H” forced PWM
3.270
3.280
3.290
3.300
3.310
3.320
0.01 0.1 1 10 100
Output Current IOUT (m A)
Output Voltage V OUT (V)
VIN=4.3V
VIN=5.0V
3.270
3.280
3.290
3.300
3.310
3.320
0 100 200 300 400 500 600
Output Current I
OUT
(m A)
Output Voltage V
OUT
(V)
VIN=4 .3 V
VIN=5 .0 V
2) Output Voltage vs. Input Voltage
RP504x VOUT=0.8V RP504x VOUT=1.2V
MODE=“H” forced PWM MODE=“H” forced PWM
0.780
0.785
0.790
0.795
0.800
0.805
0.810
0.815
0.820
22.533.544.5
Input Voltage V
IN
(V)
Output Voltage V
OUT
(V)
IOUT=1m A
IOUT=50mA
IOUT=250mA
1.180
1.185
1.190
1.195
1.200
1.205
1.210
1.215
1.220
2 2.5 3 3.5 4 4.5 5 5.5
Input Voltage V
IN
(V)
Output Voltage V
OUT
(V)
IOUT=1m A
IOUT=50mA
IOUT=250mA
RP504x VOUT=1.8V RP504x VOUT=3.3V
MODE=“H” forced PWM MODE=“H” forced PWM
1.77
1.78
1.79
1.8
1.81
1.82
1.83
22.533.544.555.5
Input Voltage V
IN
(V)
Output Voltage V
OUT
(V)
IOUT=1m A
IOUT=50m A
IOUT=250m A
3.25
3.26
3.27
3.28
3.29
3.3
3.31
3.32
3.33
3.34
3.35
3.544.555.
Input Voltage V
IN
(V)
Output Voltage V
OUT
(V)
5
IOUT=1m A
IOUT=50mA
IOUT=250mA