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Richo |
R1244N001B
1.2A, 30V Step Down DC/DC converter
NO.EA-293-111123
OUTLINE
The R1244N001B is CMOS-based Step-down DC/DC converter with an internal N-channel high side Tr.
(RDSON Typ. 0.35Ω) power switch. The R1244N001B can provide the maximum 1.2A output current. The IC
consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, phase compensation
circuits, a slope compensation circuit, a soft-start circuit, protection circuits, an internal voltage regulator, and a
switch for a bootstrap circuit. To make a step-down DC/DC converter with the R1244N001B, as external
components, an inductor, resistors, a diode, and capacitors are necessary.
The R1244N001B is a current mode PWM step-down DC/DC converter, but the external current sense resistor
is not necessary. Fast transient response and high efficiency characteristics are realized with the R1244N001B.
The R1244N001B allows the use of ceramic capacitors. The oscillator frequency is internally fixed at 1.25MHz.
Cycle by cycle current limit provides protection against over-current. Fold back circuit reduces frequency into
1/4 against shorted output and realizes limiting the Lx current. Thermal shutdown function and UVLO are also
built-in.
FEATURES
● Operating Voltage ················································ 4.5V~30V
● Internal Nch MOSFET Driver··································· Typ.RON=0.35Ω
● Adjustable output voltage with external resistor ······ 0.8V~15V
● Feed back voltage ··················································· 0.8V±1.5%
● Peak Current limit function ······································ Typ. 2.0A
● UVLO function
● Operating Frequency ··············································· 1.25MHz ( 310kHz : fold condition)
● Short protection for output ······································· Fold Back
● Ceramic Capacitor compatible
● Stand-by function ····················································· Typ. 0μA
● Package··································································· SOT-23-6W
APPLICATIONS
● 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
1
Free Datasheet http://www.Datasheet4U.com
R1244N001B
BLOCK DIAGRAMS
Thermal Shutdown
VIN
CE
UVLO
Regulator
Regulator
5V
Shutdown
Oscillator
(1250kHz
/310kHz)
SETPULSE
SD
VFB
Reference
-
+
MAXDUTY
-
+
R
Soft Start
Circuit(0.4msec) 0.8V
Current Slope
Circuit
Peak Current
Limit Circuit
BST
Lx
GND
2
Free Datasheet http://www.Datasheet4U.com
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