RICOH R1218x Technical data
R1218x SERIES
Step-up DC/DC converter for White LED Backlight
NO.EA-166-111123
OUTLINE
The R1218x Series are PWM control type step-up DC/DC converter ICs with low supply current.
The R1218x is fully dedicated to drive White LED with constant current. Each of these ICs consists of an NMOS FET, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier, a current limit circuit, an under voltage lockout circuit (UVLO), an over-voltage protection circuit (OVP).
The R1218x can drive white LEDs with high efficiency with low supply current. A diode is built-in the R1218xxx1A, therefore it is possible to drive up to 4LEDs without an external diode. The R1218xxx2A, an external diode is necessary, however, up to 7 serial LEDs can be driven with the R1218xxx2A.
Constant current can be set with an external resistance value. Dimming control is possible by PWM signal for CE pin. Feedback voltage is 0.2V, therefore power loss by current setting resistor is small and efficiency is good. Maximum duty cycle is internally fixed, Typ. 91% to 92%. LEDs can be driven from low voltage. Protection circuits are the current limit of Lx peak current, the over voltage limit of output, and the under voltage lockout function.
Packages are standard SOT-23-6 and very tiny DFN(PLP)1820-6.
FEATURES
• Input voltage.................................................. 1.8V to 5.5V
•Built-in 400mA, 1.5Ω, 20V Nch MOSFET and diode (R1218xxx1A)
•Built-in 400mA, 1.5Ω, 33V Nch MOSFET (R1218xxx2A)
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Oscillator Frequency (PWM control)............. |
1.2MHz |
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Maximum Duty Cycle .................................... |
Typ. 91% to 92% |
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Feedback Voltage ......................................... |
Typ. 0.2V |
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UVLO Threshold Voltage .............................. |
Typ. 1.6V (Hysteresis Typ. 0.1V) |
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Lx Current limit Protection............................. |
Typ. 700mA |
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Over Voltage Protection (OVP) Threshold.... |
Typ. 9.5V (R1218x021A) |
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Typ. 14.0V (R1218x031A) |
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Typ. 18.5V (R1218x041A) |
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Typ. 23.0V (R1218x052A) |
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Typ. 27.5V (R1218x062A) |
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Typ. 31.5V (R1218x072A) |
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LED dimming control..................................... |
by external PWM signal (Frequency 200Hz to 5kHz) to CE pin |
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by feedback voltage and filtered PWM signal (high frequency) |
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Packages ...................................................... |
DFN(PLP)1820-6, SOT-23-6 |
APPLICATION
• White LED Backlight for portable equipment
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R1218x |
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BLOCK DIAGRAMS |
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R1218xxx1A |
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VFB |
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VIN |
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LX |
VOUT |
Error Amp |
PWM Comp |
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UVLO |
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R |
Q |
Switch |
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OVP |
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Control |
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S |
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Vref |
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OSC |
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Slope |
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Current |
Current |
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Compensation |
Protect |
sense |
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Σ |
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Shutdown |
Chip Enable |
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delay |
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CE |
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GND |
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R1218xxx2A |
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VFB |
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VIN |
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LX |
VOUT |
Error Amp |
PWM Comp |
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UVLO |
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R |
Q |
Switch |
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OVP |
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Control |
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S |
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Vref |
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OSC |
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Slope |
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Current |
Current |
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Compensation |
Protect |
sense |
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Σ |
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Shutdown |
Chip Enable |
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delay |
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CE |
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GND |
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2
R1218x
SELECTION GUIDE
The OVP threshold, the built-in diode, and the package for the ICs can be selected at the user’s request.
Product Name |
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Package |
Quantity per Reel |
Pb Free |
Halogen Free |
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R1218Kxxxx-TR |
DFN(PLP)1820-6 |
5,000 pcs |
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Yes |
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Yes |
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R1218Nxxxx-TR-FE |
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SOT-23-6 |
3,000 pcs |
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Yes |
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Yes |
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xxxx: The combination of the OVP threshold and with/without of built-in diode can be designated. |
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Code |
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OVP Threshold |
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Built-in Diode |
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021A |
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9.5V |
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Yes |
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031A |
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14.0V |
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Yes |
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041A |
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18.5V |
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Yes |
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052A |
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23.0V |
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No |
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062A |
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27.5V |
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No |
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072A |
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31.5V |
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No |
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3
R1218x
PIN CONFIGURATIONS
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• DFN(PLP)1820-6 |
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• SOT-23-6 |
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Top View |
Bottom View |
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5 |
4 |
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6 |
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4 |
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5 |
6 |
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(mark side) |
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1 |
2 |
3 |
3 |
2 |
1 |
1 |
2 |
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PIN DESCRIPTIONS
• DFN(PLP)1820-6
Pin No |
Symbol |
Pin Description |
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CE |
Chip Enable Pin ("H" Active) |
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2 |
VFB |
Feedback Pin |
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3 |
Lx |
Switching Pin |
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(Open Drain Output) |
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GND |
Ground Pin |
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VIN |
Power Supply Input Pin |
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VOUT |
Output Pin |
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) 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.
• SOT-23-6
Pin No |
Symbol |
Pin Description |
1 |
CE |
Chip Enable Pin ("H" Active) |
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VOUT |
Output Pin |
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VIN |
Power Supply Input Pin |
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4 |
Lx |
Switching Pin (Open Drain Output) |
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5 |
GND |
Ground Pin |
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6 |
VFB |
Feedback Pin |
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4
ABSOLUTE MAXIMUM RATINGS
R1218x
(GND=0V)
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Rating |
Unit |
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VIN |
VIN Pin Voltage |
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6.5 |
V |
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VCE |
CE Pin Voltage |
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−0.3 to VIN+0.3 |
V |
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VFB |
VFB Pin Voltage |
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−0.3 to VIN+0.3 |
V |
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VOUT |
VOUT Pin Voltage |
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R1218xxx1A |
−0.3 to 22 |
V |
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R1218xxx2A |
−0.3 to 34 |
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VLX |
LX Pin Voltage |
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R1218xxx1A |
−0.3 to 22 |
V |
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R1218xxx2A |
−0.3 to 34 |
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ILX |
LX Pin Current |
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1000 |
mA |
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PD |
Power Dissipation (SOT-23-6) |
420 |
mW |
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Power Dissipation (DFN(PLP)1820-6) |
880 |
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Topt |
Operating Temperature Range |
−40 to 85 |
°C |
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Tstg |
Storage Temperature Range |
−55 to 125 |
°C |
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) 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.
5
R1218x
ELECTRICAL CHARACTERISTICS
• R1218xxxxA |
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Topt=25°C |
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Symbol |
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Conditions |
Min. |
Typ. |
Max. |
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Unit |
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VIN |
Input Voltage |
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1.8 |
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5.5 |
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V |
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IDD |
Supply Current |
VIN=5.5V, VFB=0V, Lx at no load |
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0.5 |
1.0 |
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mA |
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Istandby |
Standby Current |
VIN=5.5V, VCE=0V |
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0 |
3.0 |
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μA |
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VUVLO1 |
UVLO Detector Threshold |
VIN falling |
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1.5 |
1.6 |
1.7 |
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V |
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VUVLO2 |
UVLO Released Voltage |
VIN rising |
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VUVLO1+0.1 |
1.8 |
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V |
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VCEH |
CE Input Voltage "H" |
VIN=5.5V |
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1.5 |
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V |
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VCEL |
CE Input Voltage "L" |
VIN=1.8V |
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0.5 |
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V |
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RCE |
CE Pull Down Resistance |
VIN=3.6V |
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600 |
1200 |
2200 |
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kΩ |
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tshtdn |
CE Shutdown Delay Time |
VIN=3.6V |
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10 |
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ms |
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VFB |
VFB Voltage |
VIN=3.6V |
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0.19 |
0.20 |
0.21 |
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V |
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VFB/ |
VFB Voltage Temperature |
VIN=3.6V, −40°C ≤ Topt ≤ 85°C |
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±150 |
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ppm |
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Topt |
Coefficient |
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IFB |
VFB Input Current |
VIN=5.5V, VFB=0V or 5.5V |
−0.1 |
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0.1 |
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μA |
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RON |
Switch On Resistance |
VIN=3.6V, ISW=100mA |
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1.5 |
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Ω |
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ILXleak |
Switch Leakage Current |
R1218xxx1A |
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VLX=20V |
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0 |
3.0 |
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μA |
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R1218xxx2A |
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VLX=29V |
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0 |
3.0 |
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μA |
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ILXlim |
Switch Current Limit |
VIN=3.6V |
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400 |
700 |
1000 |
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mA |
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Vf |
Diode Forward Voltage |
R1218xxx1A |
IDIODE=100mA |
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0.8 |
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V |
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IDIODEleak |
Diode Leakage Current |
R1218xxx1A |
VOUT=20V, VLX=0V |
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10 |
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μA |
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fosc |
Oscillator Frequency |
VIN=3.6V, VOUT=VFB=0V |
1.0 |
1.2 |
1.4 |
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MHz |
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Maxduty |
Maximum Duty Cycle |
VIN=3.6V, |
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R1218x072A |
86 |
92 |
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% |
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VOUT=VFB=0V |
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Others |
86 |
91 |
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R1218x021A |
8.5 |
9.5 |
10.5 |
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R1218x031A |
13.0 |
14.0 |
15.0 |
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VOVP1 |
OVP Detector Threshold |
VIN=3.6V, |
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R1218x041A |
17.0 |
18.5 |
20.0 |
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V |
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VOUT rising |
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R1218x052A |
21.5 |
23.0 |
24.5 |
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R1218x062A |
26.0 |
27.5 |
29.0 |
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R1218x072A |
30.0 |
31.5 |
33.0 |
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R1218x021A |
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VOVP1−0.5 |
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R1218x031A |
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VOVP1−0.75 |
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VOVP2 |
OVP Released Voltage |
VIN=3.6V, |
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R1218x041A |
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VOVP1−1.0 |
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V |
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VOUT falling |
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R1218x052A |
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VOVP1−1.25 |
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R1218x062A |
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VOVP1−1.5 |
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R1218x072A |
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VOVP1−1.75 |
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