The Intersil ISL4238E, ISL4244E and ISL4245E devices are 2. 7V to 5. 5V powered RS-232 transmitters/receivers which meet ElA/TIA-232 and V. 28/V. 24 specifications, even at VCC = 3. 0V. Additionally, they provide ±15kV ESD protection (IEC61000-4-2 Air Gap and Human Body Model) on transmitter outputs and receiver inputs (RS-232 pins). Targeted applications are PDAs, Palmtops, and notebook and laptop computers where the low operational, and even lower standby power consumption is critical. Efficient on-chip charge pumps, coupled with manual and enhanced automatic power-down functions, reduce the standby supply current to a 10nA trickle. Tiny 5mmx5mm Quad Flat No-Lead (QFN) packaging and the use of small, low value capacitors ensure board space savings as well. Data rates greater than 250kbps (ISL4238E/ISL4244E)/1Mbps (ISL4245E) are guaranteed at worst case load conditions. The ISL424xE are 3 driver, 5 receiver (DTE) devices that, coupled with the QFN package, provide the industry's smallest, lowest power complete serial port suitable for PDAs, and laptop or notebook computers. The 32 Ld 5x5 QFN requires 60% less board area than a 28 lead TSSOP, and is nearly 20% thinner. The devices also include a noninverting always-active receiver for wake-up capability. The ISL4238E is a 5 driver, 3 receiver device optimized for DCE applications with full hardware handshaking. It also includes a noninverting always-active receiver for RING INDICATOR monitoring. Transmitter and logic inputs include active feedback resistors that retain the input state once driven to a valid logic level. These devices feature an enhanced automatic power-down function which powers down the on-chip power-supply and driver circuits. This occurs when all receiver and transmitter inputs detect no signal transitions for a period of 30s. These devices power back-up, automatically, whenever they sense a transition on any transmitter or receiver input. Table 1 summarizes the features of the ISL4238E, ISL4244E, ISL4245, while Application Note AN9863 summarizes the features of each device comprising the 3V RS-232 family.


  • Parameters Fully Specified for 10% Tolerance Supplies and Full Industrial Temp Range
  • Available in Small QFN (5mm x 5mm) Package which is 60% Smaller than a 28 Lead TSSOP
  • ESD Protection for RS-232 I/O Pins to ±15kV (IEC61000)
  • DTE (ISL4244E/45E) and DCE (ISL4238E) Versions
  • Lowest Supply Current in Power-down: 10nA
  • Active Feedback Resistors on TX and Logic Inputs (ISL4238E)
  • Flow Through Pinouts
  • Manual and Enhanced Automatic Power-down Features
  • Guaranteed Minimum Data Rate 250kbps (ISL4238E/ISL4244E) / 1Mbps (ISL4245E)
  • Latch-Up Free
  • On-Chip Charge Pumps Require Only Four External 0.1µF Capacitors
  • Wide Power Supply Range: Single +2.7V to +5.5V
  • Meets EIA/TIA-232 and V.28/V.24 Specifications at 3V
  • RS-232 Compatible with VCC = 2.7V
  • Pb-Free Available (RoHS Compliant)




  • Any Space Constrained System Requiring RS-232 Ports Battery Powered, Hand-Held, and Portable Equipment Laptop Computers, Notebooks PDAs and Palmtops, Data Cables Cellular/Mobile Phones, Digital Cameras, GPS Receivers


Design & Development