Part Number: LM2842XMKX-ADJL

Manufacturer: Texas Instruments

Description: Switching Voltage Regulators

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LM2842XMKX-ADJL Description

The LM284x SIMPLE SWITCHERTM devices are buck (step-down) regulators for PWM DC/DC currents. Because of their flexible operating input voltage range of 4.5 V to 42 V, they are suitable for various applications, including the conditioning of power derived from unregulated sources. They accomplish this high level of efficiency (generally 85%) by utilizing an internal switch with a low RDSON (typically 0.9 ). Operating at a frequency of either 550 kHz (with the X option) or 1.25 MHz (with the Y option) allows for more compact external components while maintaining a smooth voltage output.

The user can change the amount of time required for the soft start by connecting an external RC circuit to the shutdown (SHDN) pin. This allows the user to better tailor the computer to their specific requirements. The LM2840 can only handle a maximum load current of 100 mA, the LM2841 can handle 300 mA, and the LM2842 can take 600 mA. The value considered to be the standard nominal feedback voltage for these devices is 0.7655 V. Other features include a thermal shutdown, VIN under-voltage lockout, and gate-drive Undervoltage lockout, amongst others. You can find the LM284x in a packaging that is more efficient in its use of space called SOT-6L.

LM2842XMKX-ADJL Features

  • 5 V to 42 V Input Voltage
  • 100 mA, 300 mA, and 600 mA selectable output currents
  • Switching frequencies of 550 kHz (X) and 1.25 MHz (Y) and a feedback pin voltage of 0.765 V
  • Shutdown IQ of only 16-A typical
  • Guarded against short circuits
  • independently rewarded
  • Start-up circuitry using a gentle trigger
  • Diminutive overall solution size (SOT-6L package)
  • Use the LM2840 (or LM2841/LM2842) with the WEBENCH® Power Designer Applications to create a one-of-a-kind circuit.
  • Equipment that runs on batteries, industrial distributed power applications, portable media players, and handheld tools are all examples of standard battery-operated devices.

Features Explained in Great Detail

Input voltages from 5 V to 42 V can be accommodated by the LM284x SIMPLE SWITCHER® regulators, which are also non-synchronous step-down DC/DC converters. The devices provide high line and load regulation and can deliver DC load currents of up to 100 mA, 300 mA, or 600 mA, respectively. These gadgets can be purchased with a 550 kHz or 1.25 MHz fixed frequency. The pinout was created to facilitate an easy, optimal PCB layout, and the family’s requirements are low in terms of external components.

Characteristics Described Safety Features

The ICs in the LM284x family are guarded by specialized protective circuitry that is constantly active under normal conditions. When the temperature of the die reaches a certain threshold, the thermal shutdown circuitry cuts power to the device. When the power supply turns on or off, the UVLO comparator ensures that the power device does not operate at a voltage lower than the minimum input voltage. The MOSFET will not turn on until there is enough voltage applied to the gate drive (CB) of the device.  In shutdown mode, the supply current of an LM284x drops to about 16 A.

Modes Of Operation For Electronic Devices

Method of Constant Conduction There is a current-mode, pulse-width-modulation (PWM) buck regulator inside an LM284x. A buck regulator reduces the input voltage to produce a lower output voltage. A buck regulator runs in two cycles when operating in continuous conduction mode (where the inductor current is not allowed to drop to zero at steady-state operation). When VIN is linked to SW, the power switch is activated. The transistor is closed, and the diode is reverse-biased during the initial cycle of operation. The inductor stores energy and COUT, and the increasing current via the inductor supply the load current. Due to the inductor current’s inability to instantly reverse direction, the transistor is open, and the diode is forward-biased throughout the second cycle. The inductor stores energy, which is then transferred to the load and output capacitor. The resulting voltage will change depending on how these two cycles compare to one another.

Suggestions For A Power Source.

The input voltage range for the LM284x is 4 V to 42 V. An input supply with a voltage greater than 4.5 V and a current rating greater than the maximum input current is required. The input supply rail’s resistance must be low enough to avoid triggering a false UVLO error and the system reset during a transient in the input current. In addition to the ceramic input capacitors, bulk capacitance may be needed if the input supply is further away than a few inches.

Guidelines for Layout Layout

The feedback network’s ground side should be linked directly to the GND pin, eliminating any potential for picked-up conducted noise. To reduce the amount of noise coupled into the feedback pin, the feedback network consisting of resistors R1 and R2 should be placed near the FB pin and far from the inductor. It’s essential to have the input bypass capacitor CIN near the VIN pin. To lessen the IC’s input voltage ripple, its copper traces’ resistance is lowered. Inductor L1 should be positioned near the SW pin to reduce EM interference and capacitive coupling. Put COUT, the output capacitor, near where L1 and diode D1 connect. To minimize both conducted and radiated noise and maximize efficiency, the length of the L1, D1, and COUT traces should be kept to a minimum. To reduce conducted noise in the system ground plane, CIN, the ground connection for the diode, and COUT must be as minimal as feasible and coupled to the system ground plane in just one place (ideally at the COUT ground point).


The LM284x is a family of DC/DC regulators that perform a step-down function. They often reduce a greater DC voltage to a smaller one with an output current of 100 mA, 300 mA, or 600 mA. Choose your LM284x components using the following design technique. To develop full designs, you can also utilize the WEBENCH® program. WEBENCH uses an iterative design process and extensive component databases during the design creation process.

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