The R1205x Series are CMOS-based PWM control type step-up DC/DC converter ICs 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 Series have a 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 Series present the R1205x8xxA version that is optimized for the constant voltage power source, and the R1205x8xxB version that is optimized for driving the white LED with the constant current. The R1205x8xxB 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 Series are available in DFN1616-6B and TSOT-23-6 packages.
The Ricoh R1205x Series are CMOS-based PVVM control type step-up DC/DC converter ICs featuring low supply current. The series includes the R1205x8xxA version optimized for constant voltage power sources and the R1205x8xxB version optimized for driving white LEDs with constant current, which also supports dynamic brightness adjustment via a PWM signal.
These converters are available in DFN1616-6B and TSOT-23-6 packages. Key features include an input voltage range of 1.8V to 5.5V (for R1205x8xxB) or 2.3V to 5.5V, a typical supply current of 800µA, and built-in protection functions such as peak current limit, over-voltage protection, under-voltage lockout, and thermal shutdown.
| Input Voltage Range (R1205x8xxA) | 2.3V to 5.5V |
|---|---|
| Input Voltage Range (R1205x8xxB) | 1.8V to 5.5V |
| Supply Current (Typ.) | 800µA |
| Feedback Voltage Accuracy (R1205x8xxA) | ±1% |
| Oscillator Frequency | Typ. 1.2MHz |
| Maximum Duty Cycle | Typ. 91% |
| Over Voltage Protection (OVP) | Typ. 25V |
| Thermal Shutdown Temperature | Typ. 150°C |
| Operating Temperature Range | -40 to 85 °C |
The R1205x Series are available in DFN1616-6B and TSOT-23-6 packages.
The output voltage is calculated using divider resistors R1 and R2 with the formula: Vout = Vre x (R1+R2)/R1.