＜Analog IC＞

RT8H114C

PWM circuit

Unit：mmOUTLINE DRAWINGDESCRIPTION
RT8H114C is a PWM circuit suitable for LED drive,

2.80.65

it is possible to adjust the output duty ratio.

1.50.65

2.8CT.

FEATURES①③●The output duty ratio can be adjusted by changing the④0.81

a capacitor and resistor to the CT.
●The output can be forcibly dropped to low by applying
an input voltage to the ON/OFF.

APPLICATION

0.12●Frequency can be adjusted by externally connecting

0～0.1

1.1

DUTY voltage.

⑥114

resistance and capacitance values externally connected to the0.95 0.95

The oscillation frequency can be adjusted by changing the0.33

by changing the voltage value of the DUTY,PIN CONFIGURATION●LED drive circuit

①VCC

⑥DUTY

②OUT

⑤GND

③ON/OFFBLOCK DIAGRAM

VCC

DUTY

OUT

S

Q

R
ON/OFFCT

GND

240514

＜Analog IC＞

RT8H114C

PWM circuit

ABSOLUTE MAXIMUM RATINGS (Ta＝25℃, unless otherwise noted.)
Symbol
Vcc
VCT
VDUTY
VON/OFF
VOUT
IOUT
PdParameter
Supply voltage
CT input voltage
DUTY input voltage
ON/OFF input voltage
OUT input voltage
OUT current
Internal power dissipation

Conditions

Rating40-0.3~VCC-0.3~VCC-0.3~VCC-0.3~40
10200Unit
VVVVVmAmWKθTjTstg
Topr

Thermal derating
Junction temperature
Storage temperature
Operating temperatureTa≧25℃

1.6
150-40～150-40～150mW/℃℃℃℃(keep dry)
Not to exceed Tj (keep dry)

ELECTRICAL CHARACTERISTIC(Ta＝25℃, VCC=12V unless otherwise noted.)
Designed value
Min.
Typ.
Max.

SymbolParameter

VCC

Operating supply voltage range

61236VICC

Circuit current

0.81.0

1.5mA

Vth1

Ramp wave upper limit voltage

10.52

10.85

11.18

VVth2

Ramp wave lower limit voltage

1.216

1.280

1.344

VDuty1

ON DUTY

9.0

10.0

11.0%

Duty2

DUTY operating range

1-90%

OFFSET

DUTY offset voltage-10-10mVVosat

Output saturation voltage

-

0.20

0.35

V

VOFFTH

ON/OFF threshold voltage

1.08

1.35

1.62

VIcin

CT charge current

-

0.20

3.0uA

Icdis

CT discharge current

0.75

3.40-mA

Test condition

CT=62kΩ-VCC、0.022uF-GND

VCT=1VIOUT=3mA
VCT=2V,VDUTY=1V
VCT=1V、VDUTY=2V
VCT=6V
VCT=12V

Unit

TYPICAL CHARACTERISTIC
Thermal derating curve
250Power dissipation Pd[mW]2001501005000255075100125150

Ambient Temperature Ta[℃]240514

＜Analog IC＞

RT8H114C

PWM circuit

APPLICATION CIRCUIT EXAMPLES① When VCC is applied, the CT capacitance starts to be charged, and when theCT voltage exceeds the internal voltage 1, the internal latch circuit enters
the SET state and the CT capacitance is discharged.
② When discharging starts and the voltage of the CT falls below internal voltage 2,
the internal latch circuit becomes RESET. After that, charging and discharging are repeatedin the order of ①→②→①.
③ When the CT voltage is lower than the DUTY voltage, the OUT becomes High,and when it becomes higher than the DUTY voltage, the OUT becomes Low.
When the voltage value of the DUTY is high, the time that the OUT is High becomes longer,
so the duty ratio becomes larger. When the voltage value of the DUTY is low,
the time that the OUT is Low becomes longer, so the duty ratio becomes smaller.

240514

＜Analog IC＞

RT8H114C

PWM circuit・Setting the period of OUT voltage
The period T is determined by the sum of the time T1 and the discharge time T2 when thecharging voltage of the CT resistance RCT and capacitor CCT reaches from the lower limit(Vth2) to the upper limit (Vth1) of the CT voltage set internally in the RT8H114C. The
formula is as follows.
T1 = R CT ∙ CCT ∙ ln

VCC − Vth2
VCC − Vth1

T2 = CCT ∙ (Vth1 − Vth2 )/Icdis
T = T1 + T2
・About the DUTY ratio setting
The DUTY ratio can be set according to the DUTY voltage. The output voltage pulse
width T3 can be calculated by replacing Vth1 in the above T formula with the DUTYvoltage value.
T3 = R CT ∙ CCT ∙ ln

VCC − Vth2+ CCT ∙ (VDUTY − Vth2 )/Icdis
VCC − VDUTY

・Setting of constants for CCT and RCT

Please set the constants within the following range.
CCT：Not specified※
RCT：8 kΩ or more, 4 MΩ or less※When the CT voltage falls below Vth2 and the device switches from discharging tocharging, it is designed to switch when the voltage drops by 200ns x Icdis/CCT fromVth2 due to the response speed of the internal transistor.
The capacitance value of CCT is not specified because even a low capacitance value of

1nF or less will not affect the operation, however, the lower the capacitance value, themore pronounced the drop in CT voltage becomes.
In addition, since the comparator inside the IC is not equipped with hysteresis,
chattering may occur when the CCT capacitance value is large and the cycle is very
long, and when the CT voltage is constant near the upper limit value.
Please evaluate the setting thoroughly.
・Frequency of use
Please use frequencies of 200 kHz or less.
240514

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