1.2MHZ, 26V Step-up DC/DC Converter
Features
is a high frequency, high efficiency 2.3V to 6V input voltage Rangel The MXT7524E
DC to DC converter with an integrated 2.8A, Efficiency up to 96%
0.1Ω power switch capable of providing an
26V Boost converter with 2.8A switch
output voltage up to 26V. The fixed 1.2MHz
current allows the use of small external inductions and 1.2Mhz fixed Switching Frequency capacitors and provides fast transient response.
It integrates Soft start, Comp,. Only need few Integrated soft-start
components outside. Thermal Shutdown
Under voltage Lockout 8-Pin SOP-EPAD Package
GENERAL DESCRIPTION
APPLICATIONS
Handheld Devices GPS Receiver
Digital Still Camera Portable Applications
DSL Modem PCMCIA Card
TFT LCD Bias Supply
Figure 1Typical Application Circuit
ORDERING INFORMATION
PART NUMBER MXT7524E TEMP RANGE -40°C to 85°C SWICHING FREQUENCY 1.2MHZ OUTPUT VOLTAGE (V) ADJ ILIM (A) 2.8 PACKAGE SOP PINS 8
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MXT7524E
PIN configuration
Pin Description
PIN NAME Vin EN FB AGND PGND PGND SW SW PIN DESCRIPTION Input power supply pin Shutdown control input., Connect this pin to logic high level to enable the device Feedback pin Analog ground Power ground Power ground Switch pin Switch pin 1 2 3 4 5 6 7 8 PIN NUMBER Absolute Maximum Ratings (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.)
PARAMETER Supply Voltage VIN FB, EN Voltage SW Voltage Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Lead Temperature (Soldering, 10 sec) VALUE -0.3 to 6.5 -0.3 to VIN+0.3 Vin+0.3 to 28V -40 to 85 150 -55 to 150 300 UNIT V V V °C °C °C °C
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MXT7524E
Electrical Characteristic
parameter Input Voltage Range Boost output voltage range UVLO Threshold Operating Supply Current Shutdown Supply Current Peak Inductor Current Oscillator Frequency Rds(ON) of N-channel FET Enable Threshold Enable Leakage Current SW Leakage Current
TEST CONDITIONS Min TYP MAX unit 2.3 6.0 V 26 75 0.1 2.3 135 1 3.0 1.5 0.2 1.5 0.1 1 V V µA V A MHz Ohm V µA µA 2.1 2.2 (VIN = 3.6V, TA= 25℃C unless otherwise specified)
symbol VIN Vout VUVLO VHYSTERESIS =100mV VFB =1.3V，EN=Vin, ILoad =0 ISUPPLY VEN =0V, VIN =4.2V IPEAK FOSC ISW =-100mA VIN = 2.3V to 5.5V VEN = 0V, VSW = 0V or 5V, VIN = 5V Regulated Feedback Voltage VFB 1.188 1.2 1.212 2.5 2.8 0.9 1.2 0.3 -0.1 0.1 1 BLOCK DIAGRAM
Figure 3 Functional Block Diagram
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MXT7524E
FUNCTIONAL Description
NORMAL Operation
TS1103
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 Ton (Toff remains fixed). Some slight frequency changes might also appear with a fixed
output load 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 MXT7524E eliminates the need for an internal oscillator and slope compensation, 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 MXT7524E topology has also the benefits of providing very good load and line regulations, and excellent load transient response.
Undervoltage lockout (uvlo)
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
Thermal shutdown
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.
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MXT7524E
APPLICATION INFORMATION
INDUCTOR SELECTION
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. Selected inductor by actual application: Manufacturer Part Number Inductance (u H) 3.3 LQH44P N Murata LQH5BP 4.7 10 22 3.3 4.7 10 22 Sumida CDRH6D 23 3.3 4.7 DRC max (Ohms ) 0.065 0.08 0.16 0.37 0.044 0.058 0.106 0.259 0.11 0.16 5*5*2.4 5*5*2 4*4*1.7 Dimensions L*W*H(mm3) Table 1 Recommend Surface Mount Inductors
If output voltage is 5V or 12V，you can use 3.3μh or4.7μh 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
INPUT CAPACITOR SELECTION
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.
OUTPUT CAPACITOR SELECTION
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.
OUTPUT VOLTAGE PROGRAMMING
In the adjustable version, the output voltage is set by a resistive divider according to the following equation:
Typically choose R2=10K and determine R1 from the following equation:
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MXT7524E
TYPICAL PERFORMANCE CHARACTERISTICS
(L=4.7uH, CIN=10uF, COUT=2*10uF, if not mentioned)
Efficiency vs. Output Current (Vout=5V)
Efficiency vs. Output Current (Vout=9V)
Efficiency vs. Output Current (Vout=12V)
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MXT7524E
STARTUP (3.3V IN 5V 500MA OUT) STARTUP(3.3V IN 9V 500MA OUT)
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
PWM SWITCHING CONTINUOUS CONDUCTION MODE PWM SWITCHING DISCONTINUOUS CONDUCTION MODE
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MXT7524E
PACKAGE OUTLINE
SOP8-EPAD PACKAGE OUTLINE AND DIMENSIONS
SYMBOL A A1 A2 B C D E E1 e L θ Dimension in Millimeters MIN MAX 1.35 1.75 0.100 0.250 1.350 1.550 0.330 0.510 0.190 0.250 4.700 5.100 3.800 4.000 5.800 6.300 1.27 TYP 0.400 1.270 0o 8o Dimension in Inches MIN MAX 0.053 0.069 0.004 0.010 0.053 0.061 0.013 0.020 0.007 0.010 0.185 0.201 0.150 0.157 0.228 0.248 0.050 TYP 0.016 0.050 0o 8o
and improve the temperature of package, In order to increase the driver current capability of MXT7524E
please ensure Epad and enough ground PCB to release energy.
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