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.

Operating Voltage 5V ~ 30V
Supply Current Typ. 0.8mA (Set Vout=1.0V@Vin=30V)
Internal Nch MOSFET Driver (Ron=100mΩTyp.)
External Nch MOSFET Drive Buffer for Synchronous Operation
Adjustable Output Voltage with External Resistor 0.8V ~ 15V
Feed Back Voltage 0.8V with 1.5% accuracy
Output Current 3A *
Peak Current Limit Function Typ. 4.5A
UVLO Function
Internal Soft Start Time Typ. 0.5ms
Maximum Duty Cycle Typ. 88%
UVLO Detector Threshold Typ. 3.6V
Thermal Shutdown Function Typ. 160°C, with 30°C hysteresis
Operating Frequency Version A/B adjustable from 330kHz to 1MHz
Version C/D 330kHz
Version E/F 500kHz
Version G/H 1000kHz
Built-in Foldback Protection and its frequency 1/4 at fold condition: Ver.B
83kHz: Ver.D
125kHz: Ver.F
250kHz: Ver.H
Short Protection Function for Internal Boost Regulator
Short Protection delay time for Output Latch Typ. 5ms : Ver.A/C/E/G
Ceramic Capacitor Compatible
Stand-by Function: 0µA (Typ.) (@VIN=30V, CE="L")
Package HSOP-8E
  • *)This is an approximate value. The output current depends on conditions and external parts.
  • Power source for digital home appliance
  • Power source for hand-held communication equipment, cameras, video instruments such as VCRs, camcorders.
  • Power source for battery-powered equipment.
  • Battery Charger

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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