升压DC-DC转换芯片MXT7524E

2.3V to 6V input voltage Rangel Efficiency up to 96%

26V Boost converter with 2.8A switch

current 1.2Mhz fixed Switching Frequency Integrated soft-start

Thermal Shutdown

Under voltage Lockout 8-Pin SOP-EPAD Package

The

is a high frequency, high efficiency DC to DC converter with an integrated 2.8A, 0.1Ω power switch capable of providing an

output voltage up to 26V. The fixed 1.2MHz

allows the use of small external inductions and capacitors and provides fast transient response.

It integrates Soft start, Comp,. Only need few components outside.

Handheld Devices GPS Receiver

Digital Still Camera

Portable Applications

DSL Modem PCMCIA Card

TFT LCD Bias Supply

Figure 1Typical Application Circuit

MXT7524E

1.2MHZ, 26V Step-up DC/DC Converter

Features GENERAL DESCRIPTION

APPLICATIONS

ORDERING INFORMATION

MXT7524E

(Note: Do not exceed these limits to prevent damage to the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.)

PIN configuration Pin Description

Absolute Maximum Ratings

(V IN = 3.6V, T A= 25℃ C unless otherwise specified)

BLOCK DIAGRAM

Figure 3 Functional Block Diagram

The boost converter is designed for output voltage up to 26V with a switch peak current limit of 2.8 A.

The device, which operates in a current mode scheme with quasi-constant frequency, is externally 1.2MHZ and the minimum input voltage is 2.3 V. To control the inrush current at start-up a soft-start pin is available.

During the on-time, the voltage across the inductor causes the current in it to rise. When the current reaches a threshold value set by the internal GM amplifier, the power transistor is turned off, the energy stored into the inductor is then released and the current flows through the Schottky diode towards the output of the boost converter. The off -time is fixed for a certain Vin and Vs, and therefore maintains the same frequency when varying these parameters.

However, for different output loads, the frequency may slightly change due to the voltage drop across the Rdson of the power transistor which will have an effect on the voltage across the inductor and thus on on T (off T remains fixed). Some slight frequency changes might also appear with a fixed

output lo ad due to the fact that the output voltage Vs is not sensed directly but via the SW Pin, which affects accuracy.

Because of the quasi-constant frequency behavior of the device , the TS1103

eliminates the need for an internal oscillator and slope compensati on, which provides better stability for the system over a wide of input and output voltages range, and more stable and accurate current limiting operation compared to boost converters operating with a conventional PWM scheme .The topology has also t he benefits of providing very good load and line regulations, and excellent load transient response.

To avoid mis-operation of the device at low input voltages an under voltage lockout is included that disables the device, if the input voltage falls below 2.2V

A thermal shutdown is implemented to prevent damages due to excessive heat and power dissipation. Typically the thermal shutdown threshold is 150℃ .When the thermal shutdown is triggered the device stops switching until the temperature falls below typically 136℃.Then the device starts switching again.

FUNCTIONAL Description

NORMAL Operation

Undervoltage lockout (uvlo)

Thermal shutdown

MXT7524E MXT7524E

In normal operation, the inductor maintains continuous current to the output. The inductor current has a ripple that is dependent on the inductance value. The high inductance reduces the ripple current.

Table 1 Recommend Surface Mount Inductors

If output voltage is 5V or 12V ，you can use 3.3μh or 4.7μh or 10μh is OK, if 24V , maybe need 10μh. Normal application: Input 3.3V (3.6V or 4.2V) to Output 5V, 9V, 12V, 24V ； Input 5V to Output 9V, 12V, 24V

The input capacitor reduces input voltage ripple to the converter, low ESR ceramic capacitor is highly recommended. For most applications, a 10uF capacitor is used. The input capacitor should be placed as close as possible to VIN and GND.

A low ESR output capacitor is required in order to maintain low output voltage ripple. In the case of ceramic output capacitors, capacitor ESR is very small and does not contribute to the ripple, so a lower capacitance value is acceptable when ceramic capacitors are used. A 10uF or two 10uF ceramic output capacitor is suitable for most applications.

In the adjustable version, the output voltage is set by a resistive divider according to the following equation:

T ypically choose R2=10K and determine R1 from the following equation:

APPLICATION INFORMATION INDUCTOR SELECTION

INPUT CAPACITOR SELECTION OUTPUT CAPACITOR SELECTION OUTPUT VOLTAGE PROGRAMMING

Efficiency vs. Output Current (Vout=5V)

Efficiency vs. Output Current (Vout=9V)

Efficiency vs. Output Current (Vout=12V)

STARTUP (3.3V IN 5V 500MA OUT) STARTUP(3.3V IN 9V 500MA OUT)

PWM SWITCHING CONTINUOUS CONDUCTION MODE PWM SWITCHING DISCONTINUOUS CONDUCTION MODE

NOTES:

The efficiency is tested under normal temperature, the actual current driver capability is 70% ~90% of the max current in sheet consider of high temperature surrounding status

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In order to incr ease the driver current capability of

and improve the temperature of package, please ensure Epad and enough ground PCB to release energy.

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PACKAGE OUTLINE

SOP8-EPAD PACKAGE OUTLINE AND DIMENSIONS

MXT7524E