R1205x Series
Step-up DC / DC Converter with Overcurrent Protection
NO.EA-272-170908
OUTLINE
The R1205x is a PWM control type step-up DC/DC converter IC with low supply current. Each of these ICs
consists of an NMOS FET, a diode, 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), a soft-
start circuit, a Maxduty limit circuit, and a thermal shutdown protection circuit. This step-up DC/DC converter
can be easily built with a few external components such as a coil, a resistor, and a capacitor. As the protection
functions, the R1205x has an Lx peak current limit function, an over voltage protection (OVP) function, an
under voltage lock out (UVLO) function and a thermal shutdown function.
The R1205x presents the R1205x8xxA version that is optimized for the constant voltage power source, and
the R1205x8xxB/C version that is optimized for driving the white LED with the constant current. The
R1205x8xxB/C is an adjustable version that can change the LED brightness dynamically by using a 200Hz to
300kHz PWM signal toward the CE pin.
The R1205x is available in DFN1616-6B and TSOT-23-6 packages.
FEATURES
•
Input Voltage Range ............................................. 2.3V to 5.5V (R1205x8xxA)
1.8V to 5.5V (R1205x8xxB/C)
•
Supply Current ...................................................... Typ. 800µA
•
Standby Current .................................................... Max. 5µA
•
Feedback Voltage ................................................. 1.0V±15mV (R1205x8xxA)
0.2V±10mV (R1205x8xxB)
0.4V±10mV (R1205x8xxC)
•
Oscillator Frequency ............................................. Typ. 1.2MHz
•
Maximum Duty Cycle ............................................ Typ. 91%
•
UVLO Function ············································ Typ.2.0V (Hys.Typ.0.2V) (R1205x8xxA)
Typ.1.6V (Hys.Typ.0.1V) (R1205x8xxB/C)
•
Selectable Lx Current Limit Function .................... Typ. 350mA / 700mA
•
Over Voltage Protection ........................................ Typ. 25V
•
LED dimming control (R1205x8xxB/C) ............... by external PWM signal (Frequency 200Hz to 300kHz)
•
Thermal Protection Function ................................. Typ.150ºC(Hys.Typ.50ºC)
•
Switch ON Resistance .......................................... Typ. 1.35Ω
•
Packages .............................................................. DFN1616-6B, TSOT-23-6
•
Ceramic capacitors are recommended
APPLICATION
•
Constant Voltage Power Source for portable equipment
•
OLED power supply for portable equipment
•
White LED Backlight for portable equipment
1
R1205x
NO.EA-272-170908
SELECTION GUIDE
The OVP threshold voltage, current limit, package and V
FB
/Auto discharge are user-selectable options.
Product Name
R1205L8x1∗-TR
R1205N8x3∗-TR-FE
x
Package
DFN1616-6B
TSOT-23-6
Quantity per Reel
5,000 pcs
3,000 pcs
Pb Free
Yes
Yes
Halogen Free
Yes
Yes
: Designation of current limit.
(1) 350mA
(2) 700mA
: Designation of VFB.
(A) 1.0V
(B) 0.2V
(C) 0.4V
∗
2
R1205x
NO.EA-272-170908
BLOCK DIAGRAMS
VFB
VIN
LX
VOUT
Err. Amp.
UVLO
+
–
vref
Soft-start
PWM Comp.
+
–
R
S
Q
Driver
Control
OVP
Current
Limit
Current
sense
Thermal
Shutdown
Oscillator
Slope Com-
pensation
∑
CE
CE
VFB
Err. Amp.
R1205x8xxA
GND
LX
VOUT
VIN
UVLO
+
–
vref
PWM
Cntrl
EN
Shutdown
delay
CE
PWM Comp.
+
–
R
S
Q
Driver
Control
OVP
Current
Limit
Current
sense
Thermal
Shutdown
Oscillator
Slope Com-
pensation
∑
CE
R1205x8xxB/C
GND
3
R1205x
NO.EA-272-170908
PIN DESCRIPTIONS
DFN1616-6B
Top View
6
5
4
TSOT-23-6
Bottom View
4
5
6
6
5
4
∗
(mark side)
1
2
3
3
2
1
1
2
3
DFN1616-6B
Pin No
1
2
3
4
5
6
Symbol
CE
VFB
LX
GND
VIN
VOUT
Pin Description
Chip Enable Pin ("H" Active)
Feedback Pin
Switching Pin (Open Drain Output)
Ground Pin
Input Pin
Output Pin
∗
The tab is substrate level (GND). The tab is better to be connected to the GND, but leaving it open is also acceptable.
TSOT-23-6
Pin No
1
2
3
4
5
6
Symbol
CE
VOUT
VIN
LX
GND
VFB
Pin Description
Chip Enable Pin ("H" Active)
Output Pin
Input Pin
Switching Pin (Open Drain Output)
Ground Pin
Feedback Pin
4
R1205x
NO.EA-272-170908
ABSOLUTE MAXIMUM RATINGS
Symbol
V
IN
V
CE
V
FB
V
OUT
V
LX
I
LX
VIN Pin Voltage
CE Pin Voltage
VFB Pin Voltage
VOUT Pin Voltage
LX Pin Voltage
LX Pin Current
DFN1616-6B
(JEDEC STD. 51-7 Test Land Pattern)
TSOT-23-6
(Standard Test Land Pattern)
Item
Rating
−0.3
to 6.5
−0.3
to 6.5
−0.3
to 6.5
−0.3
to 28
−0.3
to 28
1000
2400
GND=0V
Unit
V
V
V
V
V
mA
P
D
Power Dissipation
(1)
mW
460
−40
to 125
−55
to 125
°C
°C
Tj
Tstg
Junction Temperature Range
Storage Temperature Range
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 are not assured.
RECOMMENDED OPERATING CONDITIONS
Symbol
V
IN
Ta
Item
Input Voltage (R1205x8xxA)
Input Voltage (R1205x8xxB/C)
Operating Temperature Range
Rating
2.3 to 5.5
1.8 to 5.5
−40
to 85
Unit
V
°C
RECOMMENDED OPERATING CONDITIONS
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 ratings by momentary electronic noise or surge. And the
semiconductor devices may receive serious damage when they continue to operate over the recommended operating
conditions.
(1)
Refer to
POWER DISSIPATION
for detailed information.
5
