TPS1101DR

The TPS1101DR from Texas Instruments is a 12V N-channel power distribution switch with integrated charge pump, current limiting, and fault reporting in an SOIC-8 package. The device integrates a low-RDS(on) N-channel MOSFET (78mOhm max) with all the necessary control and protection circuitry for high-side power switching applications. The internal charge pump generates the gate drive voltage above VIN, allowing the N-channel MOSFET to be fully enhanced with only 1.8V logic-level enable input, eliminating the need for an external gate drive circuit. The current limit feature (1.9A to 3.5A, typically 2.6A) protects the system from overcurrent and short-circuit conditions by limiting the output current and activating the open-drain fault flag (OC pin). The thermal shutdown circuit disables the switch when the junction temperature exceeds approximately 140C, protecting against sustained overloads. The soft-start feature controls the output voltage rise time to approximately 3.6ms, limiting inrush current into capacitive loads (such as USB bus-powered devices with bypass capacitors). The 0.05uA standby current (switch off) minimizes battery drain in always-connected applications. Reverse current blocking prevents current from flowing from the output back to the input when the switch is off. The TPS1101DR is suitable for USB power distribution, hot-swap power control, battery-powered load switching, and any application requiring a protected, logic-controlled power switch.

The TPS1101DR operates as a high-side N-channel power MOSFET switch with integrated control and protection. Key subsystems include: (1) N-Channel MOSFET – the main power switch is an N-channel MOSFET between VIN and VOUT; the 78mOhm RDS(on) minimizes voltage drop at full load (Vdrop = I x RDS(on) = 1.8A x 78mOhm = 140mV); (2) Charge Pump – an internal charge pump generates a gate voltage approximately 5V above VIN; this high gate voltage fully enhances the N-channel MOSFET (which requires VGS > VIN for high-side operation); the charge pump allows the enable input to be driven by 1.8V logic while the switch handles up to 12V; (3) Current Limit – a current-sense circuit monitors the MOSFET current; when the current exceeds the limit (1.9-3.5A), the gate drive is reduced to limit the current; the OC (overcurrent) open-drain flag is pulled low to indicate a fault; the current limit and thermal shutdown work together: if the limited current causes excessive power dissipation (V x I = (VIN-VOUT) x I_LIMIT), the junction temperature rises and thermal shutdown activates; (4) Soft-Start – when the enable pin goes high, the output voltage ramps up over approximately 3.6ms; this limits the inrush current into capacitive loads (I = C x dV/dt); without soft-start, the initial current would be limited only by the current limit, potentially stressing the device and the input supply; (5) Reverse Blocking – when the switch is off, the body diode of the N-channel MOSFET would normally conduct if VOUT > VIN; an internal reverse-blocking circuit prevents this current flow.

• USB power switch: 5V to USB port at 500mA with current limit and OC fault flag to MCU
• Hot-swap: 12V bus power switch with soft-start limiting inrush into 100uF load capacitor
• Battery load switch: 3.7V Li-Ion to subsystem at 1A with 0.05uA standby when off
• Protected power path: 5V rail with current limit and thermal shutdown for pluggable module