R1211x Series
PWM Step-Up DC/DC Controller
NO.EA-088-160113
OUTLINE
The R1211x is a CMOS-based PWM step-up DC/DC converter controller with low supply current. The R1211x
consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a reference current
unit, a protection circuit, and an under voltage lockout (UVLO) circuit. A low ripple and high efficiency step-up
DC/DC converter can be configured by only adding few external components, such as an inductor, a diode, a
power MOSFET, divider resisters, and capacitors. The R1211x002B/D has a built-in phase compensation,
while the R1211x002A/C can set a phase compensation externally. The R1211x002B/D has stand-by mode.
The max duty cycle is internally fixed at 90% typically. A soft-start function is built-in, and a soft-starting time is
set at 9 ms typically (R1211x002A/B, 700 kHz) or 10.5 ms typically (R1211xC/D, 300 kHz). The R1211x has a
latch-type protection circuit, which latches the external driver in off-state if the maximum duty cycle continues
for a specified time after soft-starting time. The protection delay time can be set with an external capacitor. To
release the protection, turn the power off and back on (power source voltage lower than UVLO detector
threshold) or make the device into standby mode and back to active mode using the CE pin.
FEATURES
• Input Voltage Range ............................................ 2.5 V to 6.0 V
• Oscillator Frequency (PWM Control) ................... 300 kHz, 700 kHz
• Maximum Duty Cycle ........................................... Typ. 90%
• Standby Current .................................................. Typ. 0 µA (R1211x002B/D)
• Feedback Voltage ................................................ 1.0 V
• Feedback Voltage Accuracy ................................ ±1.5%
• UVLO Threshold Level ........................................ Typ. 2.2 V (Hysteresis Typ. 0.13 V)
• Feedback Voltage Temperature Coefficient......... ±150 ppm/°C
• Built-in Latch-type Protection Circuit ................... Protection delay time can be set with an external capacitor
• Packages ............................................................. SON-6, SOT-23-6W
APPLICATIONS
• Constant Voltage Power Source for Portable Equipment
• Constant Voltage Power Source for LCD and CCD
1
R1211x
NO.EA-088-160113
BLOCK DIAGRAMS
R1211x002A/C Block Diagram
R1211x002B/D Block Diagram
SELECTION GUIDE
In the R1211x, the oscillator frequency, the optional function, and the package type are user-selectable options.
Selection Guide
Product Name
Package
Quantity per Reel
Pb Free
Halogen Free
R1211D002x-TR-FE
SON-6
3,000 pcs
Yes
Yes
R1211N002x-TR-FE
SOT-23-6W
3,000 pcs
Yes
Yes
x: Designation of Oscillator Frequency and Optional Function
(A) 700 kHz, with AMPOUT pin (External Phase Compensation Type)
(B) 700 kHz, with CE pin (Internal Phase Compensation Type, with Standby)
(C) 300 kHz, with AMPOUT pin (External Phase Compensation Type)
(D) 300 kHz, with CE pin (Internal Phase Compensation Type, with Standby)
2
R1211x
NO.EA-088-160113
PIN CONFIGURATIONS
Top View
6
Bottom View
6 5 4
5
4
4 5 6
∗
∗
1 2 3
(mark side)
3 2 1
2
1
SON-6 Pin Configuration
3
SOT-23-6W Pin Configuration
PIN DESCRIPTIONS
Pin Descriptions
Pin No
Symbol
R1211x002A/C
R1211x002B/D
Pin Description
SON-6
SOT-23-6W
SON-6
SOT-23-6W
DELAY
1
1
1
1
Pin for External Capacitor
(for Setting Output Delay Time of Protection)
GND
2
5
2
5
Ground Pin
EXT
3
6
3
6
External FET Drive Pin (CMOS Output)
VIN
4
4
4
4
Power Supply Pin
VFB
5
3
5
3
Feedback Pin for Monitoring Output Voltage
AMPOUT
6
2
-
-
Amplifier Output Pin
CE
-
-
6
2
Chip Enable Pin ("H" Active)
∗ Tab suspension leads in the
parts have GND level. (They are connected to the reverse side of this IC.)
Do not connect to other wires or land patterns.
3
R1211x
NO.EA-088-160113
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings
Symbol
VIN
VIN Pin Voltage
VEXT
Item
(GND = 0 V)
Unit
Rating
6.5
V
EXT Pin Output Voltage
−0.3 ~ VIN+0.3
V
VDLY
DELAY Pin Voltage
−0.3 ~ VIN+0.3
V
VAMP
AMPOUT Pin Voltage
−0.3 ~ VIN+0.3
V
VCE
CE Pin Input Voltage
−0.3 ~ VIN+0.3
V
VFB
VFB Pin Voltage
−0.3 ~ VIN+0.3
V
IAMP
AMPOUT Pin Current
±10
mA
IEXT
EXT Pin Inductor Drive Output Current
±50
mA
PD
Power Dissipation (Standard Land Pattern)*
SOT-23-6W
430
SON-6
500
mW
Topt
Operating Temperature Range
−40 ~ +85
°C
Tstg
Storage Temperature Range
−55 ~ +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.
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R1211x
NO.EA-088-160113
ELECTRICAL CHARACTERISTICS
R1211x002A Electrical Characteristics
Symbol
Item
Conditions
Min.
Typ.
(Topt = 25°C)
Max.
Unit
VIN
Operating Input Voltage
VFB
Feedback Voltage
VIN=3.3V
VFB Voltage
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
VFB Input Current
VIN=6V, VFB=0V or 6V
−0.1
Oscillator Frequency
VIN=3.3V, VDLY=VFB=0V
595
Oscillator Frequency
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
±1.4
Supply Current 1
VIN=6V, VDLY=VFB=0V,
EXT at no load
600
900
µA
Maximum Duty Cycle
VIN=3.3V,
EXT "H" side
90
94
%
REXTH
EXT "H" ON Resistance
VIN=3.3V, IEXT=−20mA
5
10
Ω
REXTL
EXT "L" ON Resistance
VIN=3.3V, IEXT=20mA
3
6
Ω
IDLY1
Delay Pin Charge Current
VIN=3.3V, VDLY=VFB=0V
2.5
5.0
7.5
µA
IDLY2
Delay Pin Discharge Current
VIN=VFB=2.5V,
VDLY=0.1V
2.5
5.5
9.0
mA
VDLY
Delay Pin Detector Threshold
VIN=3.3V,
VFB=0V,VDLY=0V→2V
0.95
1.00
1.05
V
TSTART
Soft-start Time
VIN=3.3V at 90% of
rising edge
4.5
9.0
13.5
ms
VUVLO
UVLO Detector Threshold
VIN=2.5V→2V,
VDLY=VFB=0V
2.1
2.2
2.3
V
VHYS
UVLO Detector Hysteresis
VIN=2V→2.5V,
VDLY=VFB=0V
0.08
0.13
0.18
V
IAMP1
AMP "H" Output Current
VIN=3.3V, VAMP=1V,
VFB=0.9V
0.45
0.90
1.50
mA
IAMP2
AMP "L" Output Current
VIN=3.3V, VAMP=1V,
VFB=1.1V
30
60
90
µA
∆VFB/
∆Topt
IFB
fOSc
∆fOSc/
∆Topt
IDD1
maxdty
2.5
RECOMMENDED OPERATING CONDITIONS
0.985
1.000
6.0
V
1.015
V
ppm/°
C
±150
82
700
0.1
µA
805
kHz
kHz/°C
(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
R1211x
NO.EA-088-160113
R1211x002B Electrical Characteristics
Symbol
Item
Conditions
Min.
Typ.
(Topt = 25°C)
Max.
Unit
VIN
Operating Input Voltage
VFB
Feedback Voltage
VIN=3.3V
VFB Voltage
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
IFB
VFB Input Current
VIN=6V, VFB=0V or 6V
−0.1
fOSC
Oscillator Frequency
VIN=3.3V, VDLY=VFB=0V
595
Oscillator Frequency
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
±1.4
Supply Current 1
VIN=6V, VDLY=VFB=0V,
EXT at no load
600
900
µA
Maximum Duty Cycle
VIN=3.3V, EXT "H" side
90
94
%
REXTH
EXT "H" ON Resistance
VIN=3.3V, IEXT=−20mA
5
10
Ω
REXTL
EXT "L" ON Resistance
VIN=3.3V, IEXT=20mA
3
6
Ω
IDLY1
Delay Pin Charge Current
VIN=3.3V, VDLY=VFB=0V
2.5
5.0
7.5
µA
IDLY2
Delay Pin Discharge Current
VIN=VFB=2.5V, VDLY=0.1V
2.5
5.5
9.0
mA
VDLY
Delay Pin Detector Threshold
VIN=3.3V, VFB=0V,
VDLY=0V→2V
0.95
1.00
1.05
V
TSTART
Soft-start Time
VIN=3.3V
4.5
9.0
13.5
ms
VUVLO
UVLO Detector Threshold
VIN=2.5V→2V,
VDLY=VFB=0V
2.1
2.2
2.3
V
VHYS
UVLO Detector Hysteresis
VIN=2V→2.5V,
VDLY=VFB=0V
0.08
0.13
0.18
V
ISTB
Standby Current
VIN=6V, VCE=0V
0
1
µA
ICEH
CE "H" Input Current
VIN=6V, VCE=6V
−0.5
0.5
µA
ICEL
CE "L" Input Current
VIN=6V, VCE=0V
−0.5
0.5
µA
VCEH
CE "H" Input Voltage
VIN=6V, VCE=0V→6V
1.5
VCEL
CE "L" Input Voltage
VIN=2.5V, VCE=2V→0V
∆VFB/
∆Topt
∆fOSC/
∆Topt
IDD1
maxdty
2.5
RECOMMENDED OPERATING CONDITIONS
0.985
1.000
6.0
V
1.015
V
ppm/°
C
±150
82
700
0.1
µA
805
kHz
kHz/°C
V
0.3
V
(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.
6
R1211x
NO.EA-088-160113
R1211x002C Electrical Characteristics
Symbol
Item
Conditions
Min.
Typ.
(Topt = 25°C)
Max.
Unit
VIN
Operating Input Voltage
VFB
VFB Voltage Tolerance
VIN=3.3V
VFB Voltage
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
IFB
VFB Input Current
VIN=6V, VFB=0V or 6V
−0.1
fOSC
Oscillator Frequency
VIN=3.3V, VDLY=VFB=0V
240
Oscillator Frequency
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
±0.6
Supply Current 1
VIN=6V, VDLY=VFB=0V,
EXT at no load
300
500
µA
Maximum Duty Cycle
VIN=3.3V, EXT "H" side
90
94
%
REXTH
EXT "H" ON Resistance
VIN=3.3V, IEXT=−20mA
5
10
Ω
REXTL
EXT "L" ON Resistance
VIN=3.3V, IEXT=20mA
3
6
Ω
IDLY1
Delay Pin Charge Current
VIN=3.3V, VDLY=VFB=0V
2.0
4.5
7.0
µA
IDLY2
Delay Pin Discharge Current
VIN=VFB=2.5V, VDLY=0.1V
2.5
5.5
9.0
mA
VDLY
Delay Pin Detector Threshold
VIN=3.3V, VFB=0V,
VDLY=0V→2V
0.95
1.00
1.05
V
TSTART
Soft-start Time
VIN=3.3V
5.0
10.5
16.0
ms
VUVLO
UVLO Detector Threshold
VIN=2.5V→2V,
VDLY=VFB=0V
2.1
2.2
2.3
V
VHYS
UVLO Detector Hysteresis
VIN=2V→2.5V,
VDLY=VFB=0V
0.08
0.13
0.18
V
IAMP1
AMP "H" Output Current
VIN=3.3V, VAMP=1V,
VFB=0.9V
0.45
0.90
1.50
mA
IAMP2
AMP "L" Output Current
VIN=3.3V, VAMP=1V,
VFB=1.1V
25
50
75
µA
∆VFB/
∆ Topt
∆fOSC/
∆ Topt
IDD1
maxdty
2.5
RECOMMENDED OPERATING CONDITIONS
0.985
1.000
6.0
V
1.015
V
ppm/°
C
±150
82
300
0.1
µA
360
kHz
kHz/°C
(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.
7
R1211x
NO.EA-088-160113
R1211x002D Electrical Characteristics
Symbol
Item
Conditions
Min.
Typ.
(Topt = 25°C)
Max.
Unit
VIN
Operating Input Voltage
VFB
VFB Voltage Tolerance
VIN=3.3V
VFB Voltage
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
IFB
VFB Input Current
VIN=6V, VFB=0V or 6V
−0.1
fOSC
Oscillator Frequency
VIN=3.3V, VDLY=VFB=0V
240
Oscillator Frequency
Temperature Coefficient
−40°C ≤ Topt ≤ 85°C
±0.6
Supply Current 1
VIN=6V, VDLY=VFB=0V,
EXT at no load
300
500
µA
Maximum Duty Cycle
VIN=3.3V, EXT "H" side
90
94
%
REXTH
EXT "H" ON Resistance
VIN=3.3V, IEXT=−20mA
5
10
Ω
REXTL
EXT "L" ON Resistance
VIN=3.3V, IEXT=20mA
3
6
Ω
IDLY1
Delay Pin Charge Current
VIN=3.3V, VDLY=VFB=0V
2.0
4.5
7.0
µA
IDLY2
Delay Pin Discharge Current
VIN=VFB=2.5V, VDLY=0.1V
2.5
5.5
9.0
mA
VDLY
Delay Pin Detector Threshold
VIN=3.3V, VFB=0V,
VDLY=0V→2V
0.95
1.00
1.05
V
TSTART
Soft-start Time
VIN=3.3V
5.0
10.5
16.0
ms
VUVLO
UVLO Detector Threshold
VIN=2.5V→2V,
VDLY=VFB=0V
2.1
2.2
2.3
V
VHYS
UVLO Detector Hysteresis
VIN=2V→2.5V,
VDLY=VFB=0V
0.08
0.13
0.18
V
ISTB
Standby Current
VIN=6V, VCE=0V
0
1
µA
ICEH
CE "H" Input Current
VIN=6V, VCE=6V
−0.5
0.5
µA
ICEL
CE "L" Input Current
VIN=6V, VCE=0V
−0.5
0.5
µA
VCEH
CE "H" Input Voltage
VIN=6V, VCE=0V→6V
1.5
VCEL
CE "L" Input Voltage
VIN=2.5V, VCE=2V→0V
∆VFB/
∆ Topt
∆fOSC/
∆ Topt
IDD1
maxdty
2.5
RECOMMENDED OPERATING CONDITIONS
0.985
1.000
6.0
V
1.015
V
ppm/°
C
±150
82
300
0.1
µA
360
kHz
kHz/°C
V
0.3
(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.
8
V
R1211x
NO.EA-088-160113
TYPICAL APPLICATIONS AND TECHNICAL NOTES
R1211x002A/R1211x002C Typical Application
NMOS: IRF7601 (International Rectifier)
Inductor: VLF504012MT-100M (TDK: 10 μH) R1211x002A
VLF504012MT-220M (TDK: 22 μH) R1211x002C
Diode: CRS10I30A (TOSHIBA)
C1: 4.7 μF (Ceramic)
C2: 0.22 μF (Ceramic)
C3: 10 μF (Ceramic)
C4: 680 pF (Ceramic)
C5: 2200 pF (Ceramic)
R1: Output Voltage Setting Resistor 1
R2: Output Voltage Setting Resistor 2
R3: 30 kΩ
R4: 30 kΩ
R1211x002B/R1211x002D Typical Application
NMOS: IRF7601 (International Rectifier)
Inductor: VLF504012MT-100M (TDK: 10 μH) R1211x002B
VLF504012MT-220M (TDK: 22 μH) R1211x002D
Diode: CRS10I30A (TOSHIBA)
C1: 4.7 μF (Ceramic)
R1: Output Voltage Setting Resistor 1
C2: 0.22 μF (Ceramic)
R2: Output Voltage Setting Resistor 2
C3: 10 μF (Ceramic)
R3: 30 kΩ
C4: 680 pF (Ceramic)
[Note] These example circuits may be applied to the output voltage requirement is 15 V or less. If the output
voltage requirement is 15 V or more, ratings of NMOS and diode as shown above is over the limit, therefore,
choose other external components.
9
R1211x
NO.EA-088-160113
• Use a 1 µF or more capacitance value of bypass capacitor between VIN pin and GND, C1 as shown in the
typical applications above.
• In terms of the capacitor for setting delay time of the latch protection, C2 as shown in typical applications
of the previous page, connect between Delay pin and GND pin of the IC with the minimum wiring distance.
• Connect a 1 µF or more value of capacitor between VOUT and GND, C3 as shown in typical applications
of the previous page. (Recommended value is from 10 µF to 22 µF.) If the operation of the composed
DC/DC converter may be unstable, use a tantalum type capacitor instead of ceramic type.
• Connect a capacitor between VOUT and the dividing point, C4 as shown in typical applications of the
previous page. The capacitance value of C4 depends on divider resistors for output voltage setting. Typical
value is between 100 pF and 1000 pF.
• The output voltage can be set with divider resistors for voltage setting, R1 and R2 as shown in typical
applications of the previous page. Refer to the next formula.
Output Voltage = VFB x (R1 + R2) / R2
R1 + R2 = 100 kΩ is recommended range of resistances.
• The operation of latch protection circuit is as follows: When the IC detects maximum duty cycle, charge to
an external capacitor, C2 of DELAY pin starts. And maximum duty cycle continues and the voltage of
DELAY pin reaches delay voltage detector threshold, VDLY, outputs "L" to EXT pin and turns off the external
power MOSFET. To release the latch protection operation, make the IC be standby mode with CE pin and
make it active in terms of R1211x002B/D version. Otherwise, restart with power on.
• The delay time of latch protection can be calculated with C2, VDLY, and Delay Pin Charge Current, IDLY1, as
in the next formula.
t = C2 x VDLY / IDLY1
Once after the maximum duty is detected and released before delay time, charge to the capacitor is halt
and delay pin outputs "L".
• As for R1211x002A/C version, the values and positioning of C4, C5, R3, and R4 shown in the above
diagram are just an example combination. These are for making phase compensation. If the spike noise
of VOUT may be large, the spike noise may be picked into VFB pin and make the operation unstable. In
this case, a resistor R3, shown in typical applications of the previous page. The recommended resistance
value of R3 is in the range from 10 kΩ to 50 kΩ. Then, noise level will be decreased.
• As for R1211x002B/D version, EXT pin outputs GND level at standby mode.
• Select the Power MOSFET, the diode, and the inductor within ratings (Voltage, Current, Power) of this IC.
Choose the power MOSFET with low threshold voltage depending on Input Voltage to be able to turn on
the FET completely. Choose the diode with low VF such as Shottky type with low reverse current IR, and
with fast switching speed. When an external transistor is switching, spike voltage may be generated caused
by an inductor, therefore recommended voltage tolerance of capacitor connected to VOUT is three times
of setting voltage or more.
∗ The performance of power circuit with using this IC depends on external components. Choose the most
suitable components for your application.
10
R1211x
NO.EA-088-160113
OUTPUT CURRENT AND SELECTION OF EXTERNAL COMPONENTS
Basic Circuit
Circuit through L
Discontinuous Mode
Continuous Mode
There are two modes, or discontinuous mode and continuous mode for the PWM step-up switching regulator
depending on the continuous characteristic of inductor current.
During on time of the transistor, when the voltage added on to the inductor is described as VIN, the current is
VIN x t / L. Therefore, the electric power, PON, which is supplied with input side, can be described as in next
formula.
∫
Ton
PON = V IN 2 × t/L dt ............................................................................................................................. Formula 1
0
With the step-up circuit, electric power is supplied from power source also during off time. In this case, input
current is described as (VOUT − VIN) x t / L, therefore electric power, POFF is described as in next formula.
POFF =
∫
Tf
0
VIN × (VOUT − VIN) × t/L dt ....................................................................................................... Formula 2
In this formula, Tf means the time of which the energy saved in the inductance is being emitted. Thus average
electric power, PAV is described as in the next formula.
PAV = 1/(TON + TOFF) × {
∫
Ton
0
VIN 2 × t/L dt +
∫
Tf
0
VIN × (VOUT − VIN) × t/L dt} .................................................. Formula 3
11
R1211x
NO.EA-088-160113
In PWM control, when Tf = Toff is true, the inductor current becomes continuos, then the operation of switching
regulator becomes continuous mode.
In the continuous mode, the deviation of the current is equal between on time and off time.
VIN × TON/L = (VOUT − VIN) × Toff/L .................................................................................................. Formula 4
Further, the electric power, PAV is equal to output electric power, VOUT x IOUT, thus,
IOUT = fOSC × VIN 2 × TON 2 /{2 × L × (VOUT − VIN)} = VIN 2 × TON/(2 × L × VOUT) .................................................... Formula 5
When IOUT becomes more than formula 5, the current flows through the inductor, then the mode becomes
continuous. The continuous current through the inductor is described as Iconst, then,
IOUT = fOSC × VIN 2 × TON 2 /{2 × L × (VOUT − VIN)} + VIN × Iconst/VOUT .............................................................. Formula 6
In this moment, the peak current, ILxmax flowing through the inductor and the driver Tr. is described as follows:
ILxmax = Iconst + VIN × TON/L ............................................................................................................... Formula 7
With the formula 4 and 6, ILxmax is,
ILxmax = VOUT/VIN × IOUT + VIN × TON/(2 × L) ............................................................................................. Formula 8
Therefore, peak current is more than IOUT. Considering the value of ILxmax, the condition of input and output,
and external components should be selected. In the formula 7, peak current ILxmax at discontinuous mode
can be calculated. Put Iconst = 0 in the formula. The explanation above is based on the ideal calculation, and
the loss caused by Lx switch and external components is not included. The actual maximum output current is
between 50% and 80% of the calculation. Especially, when the ILx is large, or VIN is low, the loss of VIN is
generated with the on resistance of the switch. As for VOUT, Vf (as much as 0.3 V) of the diode should be
considered.
12
R1211x
NO.EA-088-160113
TIMING CHART
R1211x002A/ R1211x002C Timing Chart
R1211x002B/ R1211x002D Timing Chart
Soft-start Operation
Soft-start operation is starting from power-on as follows:
(Step1)
The voltage level of SS is rising gradually by constant current circuit of the IC and a capacitor. VREF level which
is input to OP AMP is also gradually rising. VOUT is rising up to input voltage level just after the power-on,
therefore, VFB voltage is rising up to the setting voltage with input voltage and the ration of R1 and R2. AMPOUT
is at "L", and switching does not start.
(Step2)
When the voltage level of SS becomes the setting voltage with the ration of R1 and R2 or more, switching
operation starts. VREF level gradually increases together with SS level. VOUT is also rising with balancing VREF
and VFB. Duty cycle depends on the lowest level among AMPOUT, SS, and DTC of the 4 input terminals in the
PWM comparator.
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R1211x
NO.EA-088-160113
(Step3)
When SS reaches 1 V, soft-start operation finishes. VREF becomes constant voltage (= 1 V). Then the switching
operation becomes normal mode.
Latch Protection Operation
The operation of Latch protection circuit is as follows: When AMPOUT becomes "H" and the IC detects
maximum duty cycle, charge to an external capacitor, C2 of DELAY pin starts. And maximum duty cycle
continues and the voltage of DELAY pin reaches delay voltage detector threshold, VDLY, outputs "L" to EXT pin
and turns off the external power MOSFET. To release the latch protection operation, make the IC be standby
mode with CE pin and make it active in terms of R1211x002B/D version. Otherwise, make supply voltage down
to UVLO detector threshold or lower, and make it rise up to the normal input voltage. During the soft-start time,
if the duty cycle may be the maximum, protection circuit does not work and DELAY pin is fixed at GND level.
The delay time of latch protection can be calculated with C2, VDLY, and Delay Pin Charge Current, IDLY1, as in
the next formula.
t = C2 x VDLY / IDLY1
Once after the maximum duty is detected and released before delay time, charge to the capacitor is halt and
delay pin outputs "L".
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R1211x
NO.EA-088-160113
TEST CIRCUITS
R1211x002A/ R1211x002C Test Circuits
Oscillator Frequency, Maximum Duty Cycle,
VFB Voltage
Consumption Current
EXT "H" ON Resistance
EXT "L" ON Resistance
DELAY Pin Charge Current
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NO.EA-088-160113
DELAY Pin Discharge Current
DELAY Pin Detector Threshold Voltage
AMP "H" Output Current/
"L" Output Current
UVLO Detector Threshold/
Hysteresis Range
Soft-start Time
C1: 680 pF (Ceramic)
R1: 90 kΩ
C2: 22 μF (Tantalum) + 2.2 μF (Ceramic)
R2: 10 kΩ
C3: 2.2 μF (Ceramic) + 68 μF (Tantalum)
R3: 30 kΩ
C4: 2200 pF (Ceramic)
R4: 30 kΩ
C5: 22 μF (Tantalum)
Rout: 1 kΩ/ 330 Ω
Coil: VLF504012MT-220M (TDK: 22 μH)
Diode: CRS10I30A (TOSHIBA)
NMOS: IRF7601 (International Rectifier)
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R1211x
NO.EA-088-160113
R1211x002B/ R1211x002D Test Circuits
Oscillator Frequency, Maximum Duty Cycle,
VFB Voltage
Consumption Current
EXT "H" ON Resistance
EXT "L" ON Resistance
DELAY Pin Charge Current
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R1211x
NO.EA-088-160113
18
DELAY Pin Discharge Current
DELAY Pin Detector Threshold Voltage
Standby Current
UVLO Detector Threshold/
UVLO Hysteresis Range
CE "L" Input Current/ "H" Input Current
CE "L" Input Voltage/ "H" Input Voltage
R1211x
NO.EA-088-160113
Soft-start Time
R1: 90 kΩ
R2: 10 kΩ
R3: 30 kΩ
Rout: 1 kΩ/ 330 Ω
Coil: VLF504012MT-220M (TDK: 22 μH)
Diode: CRS10I30A (TOSHIBA)
NMOS: IRF7601 (International Rectifier)
C1: 680 pF (Ceramic)
C2: 22 μF (Tantalum) + 2.2 μF (Ceramic)
C3: 2.2 μF (Ceramic) + 68 μF (Tantalum)
C5: 22 μF (Tantalum)
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R1211x
NO.EA-088-160113
TYPICAL CHARACTERISTICS
1) Output Voltage vs. Output Current
R1211x002A
20
R1211x002A
R1211x002A
R1211x002B
R1211x002B
R1211x002B
R1211x
NO.EA-088-160113
R1211x002C
R1211x002C
R1211x002C
R1211x002D
R1211x002D
R1211x002D
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R1211x
NO.EA-088-160113
2) Efficiency vs. Output Current
R1211x002A
R1211x002A
R1211x002A
R1211x002B
R1211x002B
R1211x002B
22
R1211x
NO.EA-088-160113
R1211x002C
R1211x002C
R1211x002C
R1211x002D
R1211x002D
R1211x002D
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R1211x
NO.EA-088-160113
3) VFB Voltage vs. Input Voltage
R1211x002x
4) Oscillator Frequency vs. Input Voltage
R1211x002A/B
5) Supply Current vs. Input Voltage
R1211x002A
24
R1211x002C/D
R1211x002B
R1211x
NO.EA-088-160113
R1211x002C
6) Maximum Duty Cycle vs. Input Voltage
R1211x002A/B
R1211x002D
R1211x002C/D
7) VFB Voltage vs. Temperature
R1211x002x
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R1211x
NO.EA-088-160113
8) Oscillator Frequency vs. Temperature
R1211x002A/B
9) Supply Current vs. Temperature
R1211x002A
R1211x002C
26
R1211x002C/D
R1211x002B
R1211x002D
R1211x
NO.EA-088-160113
10) Maximum Duty Cycle vs. Temperature
R1211x002A/B
11) EXT "H" On Resistance vs. Temperature
R1211x002x
13) Soft-start Time vs. Temperature
R1211x002A/B
R1211x002C/D
12) EXT "L" On Resistance vs. Temperature
R1211x002x
R1211x002C/D
27
R1211x
NO.EA-088-160113
14) UVLO Detector Threshold vs. Temperature
R1211x002x
16) AMP "L" Output Current vs. Temperature
R1211x002A
17) DELAY Pin Charge Current vs. Temperature
R1211x002A/B
28
15) AMP "H" Output Current vs. Temperature
R1211x002A/C
R1211x002C
R1211x002C/D
R1211x
NO.EA-088-160113
18) DELAY Pin Detector Threshold vs. Temperature 19) DELAY Pin Discharge Current vs. Temperature
R1211x002x
R1211x002x
20) CE "L" Input Voltage vs. Temperature
R1211x002B/D
21) CE "H" Input Voltage vs. Temperature
R1211x002B/D
22) Standby Current vs. Temperature
R1211x002B/D
29
R1211x
NO.EA-088-160113
23) Load Transient Response
R1211x002A
R1211x002A
R1211x002B
30
R1211x
NO.EA-088-160113
R1211x002B
R1211x002B
R1211x002C
31
R1211x
NO.EA-088-160113
R1211x002C
R1211x002C
R1211x002D
32
R1211x
NO.EA-088-160113
R1211x002D
R1211x002D
24) Power-on Response
R1211x002A
R1211x002B
33
R1211x
NO.EA-088-160113
R1211x002C
R1211x002D
25) Turn-on speed with CE pin
R1211x002B
R1211x002D
34
1. The products and the product specifications described in this document are subject to change or discontinuation of
production without notice for reasons such as improvement. Therefore, before deciding to use the products, please
refer to Ricoh sales representatives for the latest information thereon.
2. The materials in this document may not be copied or otherwise reproduced in whole or in part without prior written
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3. Please be sure to take any necessary formalities under relevant laws or regulations before exporting or otherwise
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4. The technical information described in this document shows typical characteristics of and example application circuits
for the products. The release of such information is not to be construed as a warranty of or a grant of license under
Ricoh's or any third party's intellectual property rights or any other rights.
5. The products listed in this document are intended and designed for use as general electronic components in standard
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8. The X-ray exposure can influence functions and characteristics of the products. Confirm the product functions and
characteristics in the evaluation stage.
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characteristics of the products under operation or storage.
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case of recognizing the marking characteristic with AOI, please contact Ricoh sales or our distributor before attempting
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the technical information.
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Ricoh has been providing RoHS compliant products since April 1, 2006 and Halogen-free products since
April 1, 2012.
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