Texas Instruments LM5008MMX

Overview

LM5008MMX 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 off-time. It operates from 9.5 V to 95 V input, delivers regulated output via external resistor divider (FB = 2.5 V reference), and targets high-voltage industrial and telecom power rails.

For engineers reviewing the LM5008MMX datasheet, LM5008MMX pinout, LM5008MMX application, or LM5008MMX equivalent, key selection considerations include its hysteretic COT control (no loop compensation), intelligent current limit with RCL-programmable off-time, thermal shutdown at 165°C, remote shutdown via RON/SD pin, and dual-package availability in VSSOP-8 and WSON-8.

Technical Context

The LM5008MMX uses a hysteretic constant-on-time architecture where on-time varies inversely with VIN (TON = 1.25×10⁻¹⁰ × RON / VIN), enabling near-constant frequency across line and load variations. Its regulation relies on comparing FB voltage to a precision 2.5-V internal reference, while an independent 2.875-V overvoltage comparator forces immediate switch turnoff if FB exceeds threshold.

Current limiting employs a non-resettable off-timer triggered at 0.51-A typical switch current, with off-time programmable via RCL and FB voltage (Toff = 10⁻⁵ / (0.285 + (FB / 6.35×10⁻⁶ × RCL))). Startup uses an internal high-voltage series regulator (9.5 mA current-limited) to charge VCC to 6.3 V UVLO threshold before enabling the gate driver.

Key Specifications

Pinout & Package

LM5008MMX is supplied in an 8-pin VSSOP package (3.00 mm × 3.00 mm body, DGK suffix), with exposed pad not electrically connected. Pin functions are validated per TI SNVS280I datasheet Rev I.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5008MMX, LM5164PWPR offers higher current and synchronous efficiency but requires compensation and lacks native 95-V operation, while MAX17690ATP+ extends input range to 100 V but removes the intelligent RCL-based current limit and uses current-mode control-making LM5008MMX uniquely suited for simple, robust, high-voltage COT designs with minimal external parts.

Availability

LM5008MMX is available at Aetrix Electronics and suitable for industrial 48-V power distribution, telecom line card bias supplies, and automotive 24-V system post-regulators requiring stable component supply and long-term manufacturability.

Supply support for LM5008MMX 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 specializing in analog, embedded processing, and power management ICs, with leadership in high-reliability industrial and automotive solutions.

The LM5008 product line delivers high-voltage buck regulators optimized for simplicity and ruggedness in telecom, industrial, and automotive power systems-designed to minimize external components while maintaining robust protection and wide input range.

FAQ

What is the minimum input voltage required for reliable startup of the LM5008MMX?

The LM5008MMX requires a minimum input voltage of 9.5 V to initiate startup. Below this, the internal high-voltage VCC regulator cannot charge the VCC capacitor to its 6.3-V undervoltage lockout threshold, preventing the buck switch from enabling. At 9.5 V, startup is guaranteed across temperature and process variations per TI SNVS280I datasheet Section 6.3.

Can the LM5008MMX operate with an external 12-V supply connected to the VCC pin?

Yes, the LM5008MMX supports external biasing of the VCC pin with 8–14 V. When an auxiliary supply raises VCC above 7 V, the internal series regulator shuts down, reducing power dissipation and improving efficiency-especially beneficial at high VIN. The LM5008MMX datasheet explicitly permits this configuration in Section 7.3.2 and Figure 8.

How does the LM5008MMX handle short-circuit conditions on the output?

During a short circuit, the LM5008MMX triggers its intelligent current limit at ~0.51 A, immediately terminating the on-time and initiating a non-resettable off-timer. With FB ≈ 0 V, the off-time defaults to 35 µs (programmable via RCL), ensuring safe operation even at 95-V input. This prevents thermal runaway and enables automatic recovery once the fault clears-verified in TI's test data and functional description (Section 7.3.6).

What is the purpose of the BST pin on the LM5008MMX, and what capacitor value is recommended?

The BST pin on the LM5008MMX provides the floating gate drive voltage for the internal N-channel high-side buck switch. A 0.01-µF ceramic capacitor must be placed between BST and SW to supply gate charge during each on-time. This capacitor recharges through the internal diode from VCC during the off-time, and the 300-ns minimum off-timer ensures sufficient recharge time-per TI's Pin Functions table and Section 7.3.7.

Does the LM5008MMX support discontinuous conduction mode (DCM), and how does it affect light-load efficiency?

Yes, the LM5008MMX automatically operates in DCM at light loads (below half the peak-to-peak inductor ripple current). In DCM, the inductor current falls to zero each cycle, allowing pulse-skipping and reduced switching frequency-lowering switching losses and maintaining >85% efficiency even at 1-mA output. This behavior is inherent to its hysteretic COT control and confirmed in Section 7.1 and Figure 5 of the LM5008MMX datasheet.