MT2492 AEROSEMI | Alldatasheet

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Technical content

Aerosemi Technology Co., Ltd 600KHz, 16V，2A Synchronous Step-Down Converter

FEATURES

 High Efficiency: Up to 96%  600KHz Frequency Operation  2A Output Current  No Schottky Diode Required  4.5V to 16V Input Voltage Range  0.6V Reference  Slope Compensated Current Mode Control for Excellent Line and Load Transient Response  Integrated internal compensation  Stable with Low ESR Ceramic Output Capacitors  Over Current Protection with Hiccup-Mode  Thermal Shutdown  Inrush Current Limit and Soft Start  Available in SOT23-6 Package  -40°C to +85°C Temperature Range

APPLICATIONS

 Distributed Power Systems  Digital Set Top Boxes  Flat Panel Television and Monitors  Wireless and DSL Modems  Notebook Computer The MT2492 is a fully integrated, high– efficiency 2A synchronous rectified step- down converter. The MT2492 operates at high efficiency over a wide output current load range. This device offers two operation modes, PWM control and PFM Mode switching control, which allows a high efficiency over the wider range of the load. The MT 2492 requires a minimum number of readily available standard external components and is available in an 6-pin SOT23 ROHS compliant package. TYPICAL APPLICATION Figure 1. Basic Application Circuit

Aerosemi Technology Co., Ltd ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage … …… .… -0.3V to 17V Operating Temperature Range … - 40°C to +85°C BS Voltage ……….. (Vsw -0.3) to (Vsw+5V) PIN DESCRIPTION PIN NAME FUNCTION 1 BS Bootstrap. A capacitor connected between SW and BST pins is required to form a floating supply across the high-side switch driver.

2 GND Ground

3 FB Adjustable version feedback input. Connect FB to the center point of the external resistor divider. 4 EN Drive this pin to a logic -high to enable the IC. Drive to a logic -low to disable the IC and enter micro-power shutdown mode.

5 VIN Power supply Pin

6 SW Switching Pin

(MT2492)

Aerosemi Technology Co., Ltd ELECTRICAL CHARACTERISTICS (Note 3) (VIN=12V, VOUT=5V, TA = 25°C, unless otherwise noted.) Parameter Conditions MIN TYP MAX unit Input Voltage Range 4.5 16 V UVLO Threshold 4.4 V Supply Current in Operation VEN=2.0V, VFB=1.1V 0.4 0.6 mA Supply Current in Shutdown VEN =0 or EN = GND 1 uA Regulated Feedback Voltage TA = 25°C, 4.5V≤VIN ≤18V 0.588 0.6 0.612 V High-Side Switch On-Resistance 90 m Ω Low-Side Switch On-Resistance 70 m Ω High-Side Switch Leakage Current VEN=0V, VSW=0V 0 10 uA Upper Switch Current Limit Minimum Duty Cycle 3 A Oscillation Frequency 0.6 MHz Maximum Duty Cycle VFB=0.6V 92 % Minimum On-Time 60 nS Thermal Shutdown 160 ℃

Aerosemi Technology Co., Ltd TYPICAL PERFORMANCE CHARACTERISTICS VIN = 12V, VOUT = 5V, L = 10μH, TA = 25ºC, unless otherwise noted. Short protection

Figure 2. MT2492 Block Diagram with no extra external compensation components. is internally fixed to 1 ms.

Aerosemi Technology Co., Ltd MT2492 The MT2492 has cycle -by-cycle over current limit when the inductor current peak value exceeds the set current limit threshold. Meanwhile, output voltage starts to drop until FB is below the Under -Voltage (UV) threshold, typically 30% below the reference. Once a UV is triggered, the MT 2492 enters hiccup mode to periodically restart the part. This protection mode is especially useful when the output is dead-short to ground. The average shor t circuit current is greatly reduced to alleviate the thermal issue and to protect the regulator. The MT2492 exits the hiccup mode once the over current condition is removed. Startup and Shutdown If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides stable supply for the remaining circuitries. Three events can shut down the chip: E N low, VIN low and thermal shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown command. Over-Current-Protection and Hiccup

Aerosemi Technology Co., Ltd MT2492

APPLICATION INFORMATION

Setting the Output Voltage The external resistor divider is used to set the output voltage (see Typical Application on page 1). The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor. Choose R1 to be around 100 kΩ for optimal transient response. R2 is then given by: FBout VV RR Selecting the Inductor A 4.7μH to 22μH inductor with a DC current rating of at least 25% percent higher than the maximum load current is recommended for most applications. For highest efficiency, the inductor DC resistance should be less than 15mΩ. For most designs, the inductance value can be derived from the following equation. OSCLin outinout fIV VVVL ×∆× −×= )( Where ΔIL is the inductor ripple current. Choose inductor ripple current to be approximately 30% if the maximum load current, 2A. The maximum inductor peak current is: L LOADMAXL III ∆+= Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Selecting the Output Capacitor The output capacitor (C2) is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by:

11 CfRV

V Lf VV S ESR IN OUT S OUT OUT Where L is the inductor value and RESR is the equivalent series resistance (ESR) value of the output capacitor. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by:   −× ××× IN OUT S OUT OUT V V CLf VV 1 8 2 In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. F or simplification, the output ripple can be approximated to: ESR IN OUT S OUT OUT RV V Lf VV × The characteristics of the output capacitor also affect the stability of the regulation system. The MT2492 can be optimized for a wide range of capacitance and ESR values.

Aerosemi Technology Co., Ltd MT2492

PACKAGE INFORMATION

MT2492/V1.0 Xi' an Aerosemi Technology Co. , Ltd Tel: 029-88868021 0755-82879616 021-51905952 Fax: 029-88445284 0755-82877171 021-51905952 Http:// www.aerosemi.com E-mail: sales@ aerosemi.com