Ricoh launches 30V / 1A high-efficiency buck DC/DC converter for automotive applications
Ricoh Electronic Devices Co., has launched a new compact 1A synchronous buck DC/DC converter R1271, operating up to 30V (Abs. Max. 42V) input voltage. The converter features a controller and integrated high and low side N-channel MOSFETs, providing a small, high-efficiency power supply with a range of additional safety circuits, intended for consumer, industrial and automotive applications.
DC/DC converters are increasingly popular to use in many kinds of applications, as they owe their popularity in terms of efficiency, extending battery life. However, the fast switching devices make them a prime potential EMI source. Therefore the R1271 has a Spread-Spectrum Clock Generator (SSCG) for diffused oscillation frequency in PWM operation, which is available as an optional product version. The idea behind using SSCG is to modulate the clock frequency mildly, which results in spreading the EMI energy amongst many frequencies instead of concentrated at one frequency. In this way, the amount of potential interference of the base frequency and its harmonics is reduced considerably.
The device has a series of protection circuits that contributes to the application’s safe operation. The Power-Good pin provides a fault signal to the system when the device is not ready for normal use or when one of the following protection circuits or states is active:
- CE pin low, chip is disabled
- UVLO or OVLO protection active, input voltage drops below 3.3 V or rises above 35 V.
- Thermal Shutdown protection active, chip junction temperature rises above 160ºC
- Soft-Start time, during start-up or restart
- UVD & OVD active, output voltage deviates ±10% from nominal setting
- Hiccup or Latch type overcurrent protection active
As for the overcurrent protection, the designer has an option to select a product version with either Hiccup-mode or Latch mode protection, depending on the application’s requirements. Hiccup-mode overcurrent protection shuts down the chip after detecting an overcurrent condition and tries to resume to normal operation after a delay time. The Latch mode overcurrent protection will not return to normal operation automatically, but requires a reboot of the chip after removing the over-current condition.
The output current is limited by a peak current limit control method and the threshold is internally set but can be adjusted by connecting an external resistor to the LIMIT pin.
The R1271 has a special protection for cranking conditions. A power supply of automotive electronic systems can be subject to a significant input voltage drop when the engine starts. To ensure that the R1271 is able to maintain its output voltage during such event, the clock signal is linearly lowered to one-fourth of its normal frequency. This will make the on-duty larger than the normal maximum duty, which reduces the voltage difference between input and output and provides continuous operation in cold cranking condition.
The soft-start time is the time interval between controlling the CE pin to active until the output voltage reaches the set output voltage, it assures a smooth output voltage ramp up. This timing is internally set to 500 µs, but can be extended by connecting an external capacitor to the CSS pin.
Phase compensation is done internally to reduce the number of external components, another measure to design a power supply with a small PCB space.
Recommended external components are a 2.2 µH inductor and two 10 µF input and output capacitors, the R1271 is available in a compact DFN3030-12B or regular HSOP-18 package. The R1271L in a DFN3030-12B package has a special pin layout to prevent damage to the chip in the event of a short circuit between adjacent pins.
Four different product quality grades are available targeting consumer, industrial and automotive markets (AEC-Q100 compliant soon).
Input Voltage Range (Maximum Ratings): 3.6 to 30 V (42 V)
Start-up Voltage: 4.5 V
Standby Current: Typ. 4 μA
Operating Temperature Range: -40 to 105°C
Output Voltage Accuracy: ±1.0% (Ta = 25°C)
Oscillator Frequency: Typ. 2 MHz
Spread Spectrum Clock Generator (SSCG): Diffusion Rate: Typ. +10%
Minimum On-Time: Typ. 70 ns
Minimum Off-Time: Typ. 120 ns
Duty-over: Oscillation Frequency x 1 ~ 1/4
Soft start function
Thermal Shutdown: Typ. Tj = 160°C
Undervoltage Lockout (UVLO): Vcc = 3.3 V (Typ.)
Overvoltage Lockout (OVLO): Vin = 35 V (Typ.)
Overvoltage Detection (OVD): Output Voltage (Vout) +10%
LX Current Limit: Typ. 1.8 A (Limit Pin Open)
High-side MOS FET On Resistance: Typ. 0.4 Ω
Low-side MOS FET On Resistance: Typ. 0.2 Ω
Package R1271L: (L3.0 x W3.0 x H0.8 mm) DFN3030-12B
Package R1271S: (L5.2 x W6.2 x H1.45 mm) HSOP-18
Who are Ricoh?
RICOH Electronic Devices Co., LTD. is a leading global provider of semiconductor products, offering a comprehensive portfolio of CMOS Analog Power Management ICs and Real Time Clock ICs that enable engineers to design advanced applications for the consumer, industrial, and automotive markets.
Ricoh has an extensive expertise in technologies and solutions including power saving, small footprint, high performance, product longevity program, and high reliability. The company’s headquarters are based in Japan, as well as development, sales and manufacturing facilities. Regional sales and support offices are located in North America, Europe, and Asia.
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