Switched-capacitor converter for split-rail and voltage-multiplier needs
The Texas Instruments LM2660M-TI is a charge-pump voltage converter that generates a negative output equal to -Vin, a doubled positive output at 2Vin, or a halved output at Vin/2 from a single input between 1.5V and 5.5V. It delivers up to 100 mA and switches at a user-selectable 5 kHz or 40 kHz. The 8-SOIC package suits surface-mount assembly, and the -40°C to 85°C junction temperature range covers industrial control, telecom line cards, and general-purpose power-supply rails where a small, inductor-less converter is needed.
Output configuration and what it means for the rail
The LM2660M-TI is a ratiometric, fixed-output charge pump. It does not regulate against load or line variation — the output voltage tracks the input ratio (Vin/2, -Vin, or 2Vin) minus diode and switch drops. This matters for designs where a precision rail is required: the LM2660M-TI delivers a raw voltage, so a post-regulator (LDO) is needed if the load demands tight tolerance. The 100 mA output budget is the total load available; splitting that across multiple outputs (e.g., both +2Vin and -Vin) divides the current.
Switching frequency trade-off: 5 kHz vs 40 kHz
The part operates at either 5 kHz or 40 kHz, selected by an external capacitor on the FC pin. At 5 kHz, output ripple is higher but quiescent losses are lower. At 40 kHz, external flying capacitors can be smaller, saving board area, but switching losses increase.
RoHS status and sourcing consideration
The LM2660M-TI is listed as RoHS non-compliant. This is acceptable for defense, aerospace, and industrial equipment with a RoHS exemption, but it will not pass EU RoHS compliance checks for consumer or medical devices unless a specific exemption applies.