Synchronous Boost DC/DC Regulator CYT3400
Typical Applications Features
● Up to 94% Efficiency
● Low voltage start-up: 0.9V
● Shut-down current: < 1uA
● Input voltage:0.9V～4.4V
● Output voltage: 2.5V～4.3V (Up to 5Vwith
Schottky)
● Low switch on resistance Rds(ON), Internal
switch: 0.35Ω
● 1.4MHz fixed frequency switching
● Automatic PWM/PFM mode switching
● High switch on current: 1A
● Low profile SOT-23-6 package
(lead-freepackaging is now available)
Description
The CYT3400 is high efficiency synchronous, PWM step-up DC/DC converters optimized to provide a high efficient solution to medium power systems. The devices work under the input voltage between 0.9V and 4.4V with a 1.4MHz fixed frequency switching. The features minimize overall solution footprint by allowing the u of tiny, low profile inductors and ceramic capacitors. Automatic PWM/PFM mode switching at light load saves power and improve efficiency.
The CYT3400 is capable of supplying an output voltage between 2.5V and 4.3V, the internal synchronous switch is desired to provide high efficiency without Schottky.
The devices also featured providing up to 260mA from a single AA cell input or up to 600mA from a 2-cell AA with a 3V/3.3V output.
The CYT3400 regulators are available in the industry standard SOT-23-6 power packages(oruponrequest). Application
● Digital cameras and MP3
● Palmtop computers / PDAs
● Cellular phones
● Wireless handts and DSLtequila shot
modems
● PC cards
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● Portable media players
Order Information
CYT3400-○
1○2Symbol Description
①
Denotes Output voltage: A : Adjustable Output ②
Denotes Package Types: F: SOT-23-6
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Pin Assignment
Functional Diagram
PIN NUMBER
SOT-23- 6
PIN NAME FUNCTION
1 SW Switch Output
2 GND Ground
3 FB Feedback
4 EN
ON/OFF Control (High Enable)
5 Vout Output
6 Vin Input
Absolute Maximum Ratings
Electrical Characteristics
Operating Conditions: TA=25, Vin=1.2V, Vout=3.3V unless otherwi specified.
previous是什么意思PARAMETER CONDITIONS MIN TYP MAX UNITS Output Voltage Range (Adj.) 2.5 5 V Minimum Start-Up Voltage Iload=10mA 0.9 1.1 V Minimum Operating Voltage EN = Vin 0.6 0.75 V Switching Frequency 1.1 1.4 1.7 MHz Max Duty Cycle Vfb=1.15V 80 87 % Current Limit Delay to Output 40 ns Feedback Voltage 1.165 1.212 1.241 V Feedback Input Current Vfb=1.22V 1 nA NMOS Switch Leakage Vsw=5V 0.1 5 uA PMOS Switch Leakage Vsw=0V 0.1 5 uA NMOS Switch On Resistance Vout=3.3V 0.35 ΩPMOS Switch On Resistance Vout=3.3V 0.45 ΩNMOS Current Limit 700 950 mA
Quiescent Current (Active) Measured OnVout,
Nonswitching
300 500 uA
Shutdown Current Ven=0V, Including
Switch Leakage
0.1 1 uA
En Input High 1 V En Input Low 0.35 V En Input Current Ven=5.5 0.01 1 uA
Typical Performance Characteristis
Application Information
SW (Pin 1): Switch Pin.Connect inductor between SW and Vin. Keep the PCB trace lengths as short and wide as possible to reduce EMI and voltage overshoot.
美丽的星期天GND (Pin 2): Signal and Power Ground.Provide a short direct PCB path between GND and the (–) side of the output capacitor(s).
FB (Pin 3): Feedback Input to the gm Error Amplifier. Connect resistor divider tap to this pin. The output voltage can be adjusted from 2.5V to 5V by:Vout = 1.212V • [1 + (R1/R2)]
EN (Pin 4): Logic Controlled Shutdown Input. EN = High: Normal free running operation, 1.4MHz typical operating frequency. EN = Low: Shutdown, quiescent current <1µA. Output capacitor can be completely discharged through the load or feedback resistors.
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Vout (Pin 5): Output Voltage Sen Input and Drain of the Internal Synchronous Rectifier MOSFET. Bias is derived from Vout. PCB trace length from Vout to the output filter capacitor(s) should be as short and wide as possible.
Vin (Pin 6): Battery Input Voltage. The device gets its start-up bias from Vin. Once Vout exceeds Vin, bias comes from Vout. Thus, once started, operation is completely independent from Vin. Operation is only limited by the output power level and the battery’s internal ries resistance.
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PCB LAYOUT GUIDELINES
The high speed operation of the CYT3400 demands careful attention to board layout. You will not get advertid performance with careless layout. Figure 2 shows the recommended component placement.
A large ground pin copper area will help to lower the chip temperature. A multilayer board with a parate ground plane is ideal, but not absolutely necessary.
Figure 2. Recommended Component Placement for Single Layer Board
INDUCTOR SELECTION
The CYT3400 can utilize small surface mount and chip inductors due to its fast 1.4MHz switching frequency. Typically, a 2.2uH inductor is recommended for most applications. Larger values of inductance will allow greater output current capability by reducing the inductor ripple current. Increasing the inductance above 10µH will increa size while providing little improvement in output current capability.
where:
η= estimated efficiency
ccme
Ip = peak current limit value (0.6A)
Vin = input (battery) voltage
rill rillD = steady-state duty ratio = (Vout-Vin)/Vout
f = switchin
g frequency (1.4MHz typical)
L = inductance value
