Texas Instruments LM5008SDCX

Overview

LM5008SDCX from Texas Instruments is a 95-V, 350-mA constant on-time (COT) buck switching regulator with integrated 100-V N-channel MOSFET, internal 7-V VCC series regulator, and programmable current limit. It operates from 9.5 V to 95 V input, delivers regulated output via external resistor divider (FB = 2.5 V reference), and supports remote shutdown via RON/SD pin. Used in high-voltage post-regulation for telecom and automotive systems.

For engineers reviewing the LM5008SDCX datasheet, LM5008SDCX pinout, LM5008SDCX application, or LM5008SDCX equivalent, key selection considerations include its 300 ns minimum off-time, intelligent current-limit off-timer (35 µs max), 0.51 A typical current limit threshold, thermal shutdown at 165°C, and compatibility with discontinuous/continuous conduction modes across load and line variations.

Technical Context

The LM5008SDCX uses a hysteretic constant-on-time control architecture where on-time varies inversely with VIN (TON = 1.25×10⁻¹⁰ × RON / VIN), enabling near-constant frequency operation across 9.5–95 V input and load changes. Regulation relies on a 2.5 V internal reference compared against FB voltage, with overvoltage protection triggered at 2.875 V.

It integrates a floating gate driver with BST/SW bootstrap circuitry, requires no loop compensation, and implements intelligent current limiting using an external RCL resistor to set off-time (Toff = 10⁻⁵ / (0.285 + (VFB / 6.35×10⁻⁶ × RCL))). Thermal shutdown activates at 165°C with 25°C hysteresis, and VCC UVLO engages at 6.3 V with 200 mV hysteresis.

Key Specifications

Pinout & Package

LM5008SDCX is packaged in an 8-pin WSON (NGU) with 4.00 mm × 4.00 mm body size and exposed thermal pad (EP) connected to system ground. The package provides low thermal resistance (RθJA = 42°C/W) and optimized layout for high-voltage buck conversion.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck regulator applications.

Compared with LM5008SDCX, LM5164QDDARQ1 adds automotive qualification and frequency flexibility at the cost of compensation design effort, while MAX17690ATP+T trades integrated bias regulation and adaptive current limiting for smaller solution size and fixed-frequency predictability.

Availability

LM5008SDCX is available at Aetrix Electronics and suitable for telecom power conversion, automotive high-voltage post-regulation, and industrial sensor power supply requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM5008SDCX includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and communications markets.

The LM5008 product line delivers high-voltage DC/DC buck regulators targeting cost-sensitive, space-constrained applications where simplicity, reliability, and wide input range are critical-especially in telecom infrastructure and 48-V automotive subsystems.

FAQ

What is the recommended minimum load current for stable operation of the LM5008SDCX?

The LM5008SDCX requires a minimum load current of 1 mA to maintain proper bootstrap capacitor charge and prevent low-frequency cycling or shutdown. This is typically ensured by selecting feedback resistors (R1/R2) with sufficiently low values to draw ≥1 mA at nominal VOUT. For example, a 10 V output with R2 = 1 kΩ draws 2.5 mA through the divider, satisfying this requirement without additional loading.

How does the LM5008SDCX implement current limiting, and what role does the RCL pin play?

The LM5008SDCX uses an intelligent current limit that terminates the on-time when switch current exceeds 0.51 A (typ), then initiates a non-resettable off-time controlled by the RCL pin. An external resistor between RCL and RTN sets the off-duration based on FB voltage: Toff = 10⁻⁵ / (0.285 + (VFB / 6.35×10⁻⁶ × RCL)). At VFB = 0 V (e.g., short circuit), Toff defaults to 35 µs-ensuring safe operation up to 95 V input.

Can the LM5008SDCX operate without an external bootstrap capacitor?

No-the LM5008SDCX requires a 0.01 µF ceramic capacitor between BST and SW pins for proper high-side gate drive. During each off-time, the internal diode charges this capacitor from VCC; the 300 ns minimum off-time ensures adequate recharge. Omitting the capacitor causes gate drive failure, switch malfunction, and potential device damage. The BST pin has no internal capacitance and cannot function without this external component.

What is the purpose of the RON/SD pin, and how is shutdown implemented?

The RON/SD pin serves dual functions: setting on-time (via resistor to VIN) and enabling remote shutdown. When pulled below 0.7 V (typ), the LM5008SDCX enters shutdown mode-disabling both the buck switch and internal VCC regulator-reducing input current to 76 µA (typ). This pin must not be left floating; a pull-down resistor or active-low control signal is required for reliable shutdown behavior.

Does the LM5008SDCX require output capacitor ESR for stable regulation, and why?

Yes-the LM5008SDCX's hysteretic control requires a minimum 25–50 mV of ripple voltage at the FB pin for reliable regulation. This ripple is generated by output capacitor ESR interacting with inductor current ripple. If low-ESR ceramic capacitors are used, a small series resistor (R3 in TI's Figure 7) must be added to ensure sufficient FB ripple; otherwise, regulation becomes unstable or oscillatory due to insufficient hysteresis trigger margin.