RICOH R1242S Series Data Sheet

R1242S Series

3A∗ 30V Input PWM Step-down DC/DC Converter with Synch. Rectifier Ext. Low-side Tr.

The R1242S Series are 30V input, CMOS-based PWM step-down DC/DC converters featuring 3A∗ output current. R1242S includes a soft start circuit and a latch or fold-back protection circuit. By simply using an inductor, resistors, a low side switch (FET), and capacitors as external components, a high-efficiency step-down DC/DC converter can be easily configured. Due to current mode PWM control, the R1242S provides a fast response and high efficiency. Ceramic output capacitors can be used.

FEATURES • Supply Current (IDD) ························Typ. 0.8m A (VIN=30V, SET VFB=1.0V) • Soft Start Time (tstart) ·······················Typ. 0.5ms • Standby Current (Istandby) ·················Max. 20μA (VIN=30V, CE="L") • High Side Switch Limit Current ·······Typ. 4.5A • Input Voltage Range (VIN) ···············5.0V to 30.0V • Thermal Shutdown Circuit ··············Stops at 160°C • Output Voltage Range (VOUT)··········0.8V to 15.0V (externally adjustable) • Latch Protection Circuit···················Delay time for protection (Feedback voltage : 0.8V) Typ. 5ms (A/C/E/G Version) • Feedback Voltage Accuracy ···········± 12m V • Fold-back Protection Circuit············Fold-back frequency • Output Current (IOUT)·······················3A∗ fosc × 1/4 (B Version), • Oscillator Frequency (fosc)···············Select from 330k Hz to 1MHz with an external 83k Hz (D Version), resistor (A/B Version), 125k Hz (F Version), 330k Hz (C/D), 500k Hz (E/F), or 1MHz (G/H) 250k Hz (H Version) • Oscillator Maximum Duty Cycle (Maxduty) ···Typ. 88% • Package··········································HSOP-8E • UVLO Detect Voltage (VUVLO) ·········Typ. 3.6V

∗) This is an approximate value, because output current depending on conditions and external parts.

BLOCK DIAGRAM TYPICAL APPLICATION

R1242S001A R1242S001A/B Efficiency vs. Output Current

Thermal Shutdown VIN

R1 VIN BST

5V 50kΩCSPD CBST

CE UVLO Regulator Regulator CIN

VOUT=3.3V

ffi ci en cy BST

Shutdown

SETPULSE L4.7μH

D S COUT

RT OSC

LX EXT

VFB MAXDUTY

GND CE

at short 1000k Hz GND "H"active

Soft Start

0.8V (Recommendation)

Current Slope Limit Latch

CSPD: Speed-up capacitor Peak Current Limit Shutdown CIN, COUT: Ceramic capacitors can be used. CBST: Bootstrap Capacitor R1, R2: Resistors for setting output voltage

SELECTION GUIDE

.C. : 330k Hz, Latch type

Halogen Free Package Q'ty per Reel Part No.

.D. : 330k Hz, Fold-back type

HSOP-8E 1,000 pcs R1242S001.∗ -E2-FE .E. : 500k Hz, Latch type

.F.. : 500k Hz, Fold-back type

.∗ : Specify a combination of the oscillator frequency and the protection circuit.

.G. : 1MHz, Latch type

.A. : Oscillator Frequency adjustable, Latch type

.H. : 1MHz, Fold-back type

.B. : Oscillator Frequency adjustable, Fold-back type

PACKAGE TYPICAL CHARACTERISTIC

HSOP-8E R1242S Efficiency vs. Output Current

VOUT=3.3V, fosc=500k Hz

Top View Bottom View

1 CE (Synchronous rectification)

2 EXT 3 BST 4 VIN 5 Lx

4 2 1 3 1 3 4 2 VIN=5V

6 GND

VIN=9V VIN=12V

∗) The tab is substrate level (GND). 7 VFB

VIN=24V

∗2) The TEST pin connected to the GND level or VIN=30V

8 RT or TEST∗2

should be open.

Output Current IOUT (m A)

APPLICATIONS • Power source for digital home appliances such as digital TVs and DVD players • Power source for hand-held communication equipment, cameras, and VCRs • Power source for office automation equipment such as printers and fax machines • Power source for battery-powered equipment No.EK-191-111001 Step-down DC/DC Converter