The R1204x Series is a low-supply-current CMOS-based PWM step-up DC/DC converter. Internally, a single IC 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), a soft-start circuit, a maximum duty cycle limit circuit, and a thermal shutdown protection circuit. By simply using an inductor, a resistor, capacitors and a diode as external components, a high-efficiency step-up DC/DC converter can be easily configured. As protection functions, the IC contains a thermal shutdown protection circuit, a current limit circuit, an OVP circuit, and an UVLO circuit. A thermal shutdown circuit detects overheating of the ICs and stops the operation to protect it from damage. A current limit circuit limits the peak current of Lx, and an OVP circuit detects the over voltage of output, and an UVLO circuit detects the low input voltage. The R1204x Series provide the R1204xxxA/D versions, which are optimized for serial driving of white LEDs with constant current, and the R1204xxxB/C/E/F versions, which are optimized for constant voltage driving. Among the R1204xxxB/C/E/F versions, only the R1204xxxC/F versions are equipped with PWM/VFM auto switching controls. The LED current can be determined by the value of current setting resistor. The brightness of the LED can be adjusted by changing the value of the current setting resistor.
The R1204x Series are low supply current CMOS-based PWM step-up DC/DC converters. Internally, a single IC 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), a soft-start circuit, a maximum duty cycle limit circuit, and a thermal shutdown protection circuit.
The series provides R1204xxxA/D versions optimized for serial driving of white LEDs with constant current, and R1204xxxB/C/E/F versions optimized for constant voltage driving. Among the latter, only R1204xxxC/F versions are equipped with PWM/VFM auto-switching controls.
| Input Voltage Range | 2.3V to 5.5V |
|---|---|
| Supply Current (Typical) | 800uA |
| Feedback Voltage (R1204xxxxB/C/E/F) | 1.0V +/- 15mV |
| Lx Current Limit Function | Min. 700mA |
| Over Voltage Protection Thresholds | 23V, 33V, 42V (+1.5V) |
| Oscillator Frequency (R1204xxxxA/B/C) | Typ. 1.0MHz |
| FET ON Resistance | Typ. 0.8 Ohm |
| Operating Temperature Range | -40 to +85 °C |
The R1204xxxA/D versions are optimized for serial driving of white LEDs with constant current.
Only the R1204xxxC/F versions among the constant voltage optimized series (B/C/E/F) are equipped with PWM/VFM auto-switching controls.
The recommended bypass capacitor value is 1.0uF.