SP3232EEY-L

The SP3232EEY-L is a true RS-232 transceiver from MaxLinear’s SP3232E series, providing 2 drivers and 2 receivers in a single TSSOP-16 package. It is designed for portable and handheld applications requiring RS-232 communication from 3.3-V or 5-V logic supplies.

The integrated charge pump doubles and inverts the supply voltage to generate the ±5.4-V (typical) RS-232 output levels required by EIA/TIA-232-F, using only four 0.1-µF external capacitors. This is a significant improvement over older designs requiring 1-µF capacitors, reducing board area and cost.

The device meets all EIA/TIA-232-F specifications with a minimum data rate of 120 kbps under full 3-kΩ/1000-pF load, sufficient for standard serial communication up to 115.2 kbps with margin. The driver output swing exceeds ±5.0 V with a 3-kΩ load, ensuring compatibility with all standard RS-232 receivers.

ESD protection is a standout feature: ±15-kV Human Body Model, ±15-kV IEC 61000-4-2 air discharge, and ±8-kV IEC 61000-4-2 contact discharge on all RS-232 pins. This eliminates the need for external TVS diodes in most applications, simplifying the BOM.

The EEY-L suffix denotes: E = enhanced ESD version, Y = TSSOP-16 package, -L = -40°C to +85°C industrial temperature range, tape and reel. The SP3232E does not include shutdown or tri-state features (those are on the SP3222E variant). Supply current is 0.3 mA typical at no load with 3.3-V supply, making it suitable for always-on serial ports in battery-powered devices.

**Charge Pump (Voltage Doublers):** The SP3232E uses a regulated dual charge pump to generate RS-232 voltage levels from a single 3.0-5.5-V supply. The first stage is a voltage doubler (C1 charge pump) that produces V+ ≈ 2 × VCC from the C1+/C1- pins. The second stage is a voltage inverter (C2 charge pump) that produces V- ≈ -2 × VCC from the C2+/C2- pins. A V+ storage capacitor (C3) and V- storage capacitor (C4) smooth the outputs. Regulation limits V+ and V- magnitudes to approximately 5.5 V to prevent exceeding RS-232 maximums.

**Driver Stage:** Each driver converts TTL/CMOS logic levels (0.8-V low, 2.4-V high thresholds) to RS-232 levels (±5.4-V swing typical). When the logic input is high, the output swings negative; when low, the output swings positive (inverting). The output is current-limited and can drive a 3-kΩ load with 1000-pF cable capacitance.

**Receiver Stage:** Each receiver converts RS-232 input levels (±3-V to ±15-V range) to TTL/CMOS logic levels. The input threshold is 0.8-V TTL compatible with 0.5-V typical hysteresis for noise immunity. A 5-kΩ pull-down resistor to ground on each receiver input ensures a defined logic-high output when the RS-232 cable is disconnected.