TCS3354_DCDC_1.5A_升压SOT23-5

• Integrated 0.5Ω Power MOSFET • 40μA Quiescent Current • 2.5V to 5.5V Input Voltage

• 1.2MHz Fixed Switching Frequency • Internal 1.5A Switch Current Limit • Adjustable Output Voltage • Internal Compensation • Up to 28V Output Voltage

• Automatic Pulse Frequency Modulation Mode at Light Loads • Over 85% Efficiency

• Available in a 5-Pin TSOT23-5 Package

GENERAL DESCRIPTION

The TCS3354 is a constant frequency, 5-pin TSOT23 current mode step-up converter intended for small, low power applications. The TCS3354 switches at 1.2MHz and allows the use of tiny, low cost capacitors and inductors 2mm or less in height. Internal soft-start results in small inrush current and extends battery life. The TCS3354 operates from an input voltage as low as 2.5V and can generate 28V at up to 100mA from a 5V supply.

The TCS3354 features automatic shifting to pulse frequency modulation mode at light loads. The TCS3354 includes under-voltage lockout, current limiting, and thermal overload protection to prevent damage in the event of an output overload. The TCS3354 is available in a small 5-pin TSOT-23 package.

APPLICATIONS

• OLED Biasing • LCD Bias Supply • White LED Driver • PDAs

• Digital Still Cameras

Typical Application

Efficiency

Iout (mA)

Figure 2. Efficiency Curve

Figure 1. Basic Application Circuit

Rev.1.0 Jan.20,2011 Page 1 1.5A, 1.2MHz,Up to 28V Output Micropower Step-up Converter TCS3354Absolute Maximum Ratings

Input Supply Voltage …………… -0.3V to 6V SW Voltage ……………………..-0.3V to 30V Operating Temperature ..…. -40°C to +85°C EN, FB Voltages .........................-0.3V to 6V Junction Temperature ………………...160°C

Storage Temperature Range -65°C to 150°C Peak SW Sink and Source Current ……1.8A Lead Temperature(Soldering,10s) ...+300°C

Package/Order Information

Pin Description

PIN NAME FUNCTION

Power Switch Output. SW is the drain of the internal MOSFET switch.

1 2 3

SW GND FB

Connect the power inductor and output rectifier to SW. SW can swing between GND and 28V. Ground Pin

Feedback Input. The FB voltage is 1.23V. Connect a resistor divider to FB.

Regulator On/Off Control Input. A high input at EN turns on the converter, and a low input turns it off. When not used, connect EN to the input supply for automatic startup. Input Supply Pin. Must be locally bypassed.

4 5

EN IN

Rev.1.0 Jan.20,2011 Page 2 1.5A, 1.2MHz,Up to 28V Output Micropower Step-up Converter TCS3354ELECTRICAL CHARACTERISTICS

(VIN=VEN=3.7V, TA = 25°C, unless otherwise noted.)

Parameter

Operating Input Voltage Under Voltage Lockout

Under Voltage Lockout Hysteresis Current (Shutdown) Quiescent Current (PFM) Quiescent Current (PWM) Switching Frequency Maximum Duty Cycle EN Input High Voltage EN Input Low Voltage FB Voltage FB Input Bias Current SW On Resistance (1) SW Current Limit (1) SW Leakage Thermal Shutdown Note:

1) Guaranteed by design, not tested.

VEN= 0V

VFB=1.4V，No switch VFB=1V，switch VFB= 0V VFB= 1.23V

VIN= 4.2V, Duty cycle=50%VSW = 20V

Conditions

MIN 2.5 90 1.5 1.176 -50

TYP 2.2 100 0.1 40 0.6 1.2 1.23 -10 0.5 1.5 155

MAX unit5.5 2.45 1 60 1 0.4 1.254 1

V V mVµA µA mAMHz% V V V nA ΩA μA℃

Rev.1.0 Jan.20,2011 Page 3 1.5A, 1.2MHz,Up to 28V Output Micropower Step-up Converter TCS3354OPERATION

The TCS3354 uses a fixed frequency, peak current mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the TCS3354 can be understood by referring to the block diagram of Figure 3. At the start of each oscillator cycle the MOSFET is turned on through the control circuitry.

To

prevent

sub-harmonic

oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current sense amplifier and the result is fed into the negative input of the PWM comparator. When this voltage equals

the output voltage of the error amplifier the power MOSFET is turned off. The voltage at the output of the error amplifier is an amplified version of the difference between the 1.23V bandgap reference voltage and the feedback voltage. In this way the peak current level keeps the output in regulation. If the feedback voltage starts to drop, the output of the error amplifier increases. This results in more current to flow through the power MOSFET, thus increasing the power delivered to the output. The TCS3354 has internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the output.

Figure 3. Functional Block Diagram

Rev.1.0 Jan.20,2011 Page 4 1.5A, 1.2MHz,Up to 28V Output Micropower Step-up Converter TCS3354Typical Operating Characteristics

Efficiency Curve

Current limit vs. Vin

Iout (mA)

Vin (V)

Power On/Off from EN Load Transient Response

Time （1ms/Div）Time （400us/Div）

Normal Operation

Time （800ns/Div）

Rev.1.0 Jan.20,2011 Page 5 1.5A, 1.2MHz,Up to 28V Output Micropower Step-up Converter TCS3354APPLICATION INFORMATION

Setting the Output Voltage

The internal reference VREF is

1.23V(Typical).The output voltage is divided by a resistor divider,R1 and R2 to the FB pin.The output voltage is given by

Layout Consideration

For best performance of the TCS3354, the following followed.

Input and Output capacitors should be guidelines

must

be

strictly

Inductor Selection

The recommended value of inductor are 4.7 to 22μH. Small size and better efficiency are the major concerns for portable device, such as TCS3354 used for mobile phone. The

inductor should have low core loss at 1.2MHz and low DCR for better efficiency. To avoid inductor saturation current rating should be considered.

Capacitor Selection

Input and output ceramic capacitors of 1μFare recommended for TCS3354 applications. For better voltage filtering, ceramic capacitors with low ESR are recommended. X5R and X7R types are suitable because of their wider voltage and temperature ranges.

Diode Selection

Schottky diode is a good choice for TCS3354because of its low forward voltage drop and fast reverse recovery. Using Schottky diode can get better efficiency. The highspeed rectification is also a good characteristic of Schottky diode for high switching frequency. Current rating of the diode must meet the root mean square of the peak current and output average current multiplication as following :

The diode’s reverse breakdown voltage should be larger than the output voltage.

Rev.1.0 Jan.20,2011 Page 6 placed close to the IC and connected to ground plane to reduce noise coupling. The GND should be connected to a strong ground plane for heat sinking and noise protection. Keep the main current traces as possible as short and wide.

SW node of DC-DC converter is with high frequency voltage swing. It should be kept at a small area.

Place the feedback components as close as possible to the IC and keep away from the noisy devices.

1.5A, 1.2MHz,Up to 28V Output Micropower Step-up Converter TCS3354PACKAGE INFORMATION

Rev.1.0 Jan.20,2011 Page 7