R1242S Series

30V Input 3A Buck DC/DC converter

Data Sheet / Flyer
Data Sheet * Flyer

The R1242S Series are CMOS-based 30V Input, 3A, Synchronous Rectified Step-down DC/DC Converters with built-in Highside Switch. Each of these ICs contains Nch Highside Tr. (Typ. 0.1Ω) and can supply maximum 3A output current. In order to reduce heat generation caused by energy loss, FET can be used as Lowside switch. Lowside switch turns off when ICs shut down. Each of these ICs consists of the followings: an oscillator, a PWM control circuit, a voltage reference unit, an error amplifier, a phase compensation circuit, a slope control circuit, a soft-start circuit, protection circuits, an internal regulator, a switch, and so on. Also, each of these ICs consists of the following external components: an inductor, resistors, an external FET, and capacitors.

The R1242S Series operates with Current Mode Topology, which does not require any sense resistor. As a result, these ICs can achieve high speed and high efficiency. The oscillator frequencies for each version are set as follows; adjustable between 330kHz to 1000kHz for versions A and B, 330kHz for versions C and D, 500kHz for versions E and F, and 1000kHz for versions G and H.

Each of these ICs are equipped with the protection functions, such as Peak Current Limit function, Latch function, Fold back function, Thermal-Shutdown function, and Undervoltage-Lockout (UVLO) function. Peak Current Limit function restricts the maximum current into 4.5A. Latch function (comes with versions A, C, E, and G) shuts off the output if current limit detection continues for a certain period of time. Fold back function (comes with versions B, D, F, and H) reduces the initial oscillator frequencies into 1/4 when output is short-circuited.

Supply Current Typ. 0.8 mA (VIN = 30 V, Set VFB = 1.0 V)
Standby Current Typ. 0 µA (VIN = 30 V, CE = L)
Input Voltage Range 5 V to 30 V
Output Voltage Range 0.8 V to 15 V, Adjustable using external resistors
Feed Back Voltage Accuracy 0.8 V with 1.5% accuracy
Output Current 3 A*
Oscillator Frequency 330 kHz to 1 MHz (Ver. A/B), 330 kHz (Ver. C/D),
500 kHz, (Ver. E/F), 1000 kHz (Ver. G/H)
Maximum Duty Cycle Typ. 88%
UVLO Detector Threshold Typ. 3.6 V
Soft-start Time Typ. 0.5 ms
Peak Current Limit Typ. 4.5 A
Thermal Shutdown Typ. 160°C
Latch Type Protection Delay Time: Typ. 5 ms (Ver. A/C/E/G)
Fold-back Type Protection Fold-back Frequency: Ver. B: fosc x 1/4,
Ver. D: 83 kHz, Ver. F: 125 kHz, Ver. H: 250 kHz
Package HSOP-8E
  • *)This is an approximate value. The output current depends on conditions and external parts.
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Data Sheet Flyer Design Guide
R1242S Series R1242S Series R1242S Series
Package Info. Mark Info. Quality Assurance Data
HSOP-8E R1242S Reliability

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