Application Note: AN_SY8081
High Efficiency 2.5MHz, 1A Synchronous Step Down Regulator
General Description
SY8081 is a high efficiency 2.5MHz synchronous step down DC/DC regulator IC capable of delivering up to 1A output currents. It can operate over a wide input voltage range from 2.5V to 5.5V and integrate main switch and synchronous switch with very low RDS (ON) to minimize the conduction loss.
Features
• Low RDS(ON) for internal switches (top/bottom) 230mΩ/150mΩ • 2.5~5.5V input voltage range • High switching frequency 2.5MHz minimizes the external components • Internal soft-start limits the inrush current • RoHS Compliant and Halogen Free • Output auto discharge function • 100% dropout operation
SY8081 □(□□)□ Temperature Code Package Code Optional Spec Code Temperature Range: -40°C to 85°C Ordering Number SY8081DQC Package Type DFN1.5×1.5-6 Note 1A
Applications
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Figure1. Schematic Diagram
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Typical Applications
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• • • • •
Portable Navigation Device Set Top Box USB Dongle Media Player Smart phone
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• Compact package: DFN1.5x1.5-6
AN_SY8081 Rev. 0.9
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Ordering Information
Figure2. Efficiency
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AN_SY8081
Pinout (Top View)
Top Mark: MNxyz (device code: MN, x=year code, y=week code, z= lot number code)
EN PGND SGND LX IN FB
1 5 2 4 6 3
Enable control. Pull high to turn on. Do not float. Power ground pin. Signal ground pin.
Inductor pin. Connect this pin to the switching node of inductor. Input pin. Decouple this pin to GND pin with at least 10uF ceramic cap. Output Feedback Pin. Connect this pin to the center point of the output resistor divider (as shown in Figure 1) to program the output voltage: VOUT=0.6*(1+R1/R2).
Supply Input Voltage ----------------------------------------------------------------------------------------------- 2.5V to 5.5V Junction Temperature Range ----------------------------------------------------------------------------------- -40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------ -40°C to 85°C
AN_SY8081 Rev. 0.9
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Recommended Operating Conditions (Note 3)
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Supply Input Voltage -------------------------------------------------------------------------------------------------------- 6.0V Enable, FB Voltage---------------------------------------------------------------------------------------------------- VIN + 0.6V Power Dissipation, PD @ TA = 25°C, DFN1.5×1.5-6 ------------------------------------------------------------------------------------------------------ 1.6 W Package Thermal Resistance (Note 2) θ JA ----------------------------------------------------------------------------------------------------------------145°C/W θ JC -----------------------------------------------------------------------------------------------------------------81°C/W Junction Temperature Range ----------------------------------------------------------------------------------------------125°C Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------------------- 260°C Storage Temperature Range ----------------------------------------------------------------------------------- -65°C to 150°C
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Absolute Maximum Ratings (Note 1)
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Pin Name
Pin Number
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2厦门 雾霾
(DFN1.5x1.5-6)
AN_SY8081
Electrical Characteristics
(VIN = 5V, VOUT = 2.5V, L = 1.0uH, COUT = 4.7uF, TA = 25°C, unless otherwise specified)
Parameter Input Voltage Range Quiescent Current Shutdown Current Feedback Reference Voltage FB Input Current PFET RON NFET RON PFET Current Limit EN rising threshold EN falling threshold Input UVLO threshold UVLO hysteresis Oscillator Frequency Min ON Time Max Duty Cycle Soft Start Time Thermal Shutdown Temperature Thermal Shutdown Hysteresis Output discharge resistor
Symbol VIN IQ ISHDN VREF IFB RDS(ON),P RDS(ON),N ILIM VENH VENL VUVLO VHYS FOSC TSS TSD THYS RDSC
Test Conditions IOUT=0, VFB=VREF ⋅ 105% EN=0 VFB=VIN
Min 2.5
Typ 40 0.1 0.6 230 150
Max 5.5 1 0.612 50
0.588 -50
Unit V µA µA V nA mΩ mΩ A V V V V MHz ns % ms °C °C Ω
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100
1.3 1.5
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0.4 2.5 0.1 2.5 65 1 160 15 120
Note 2: θ JA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Exposed Paddle of DFN package is the case position for θ JC measurement. Note 3: The device is not guaranteed to function outside its operating conditions.
AN_SY8081 Rev. 0.9
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Silergy Corp. Confidential- Prepared for Customer Use Only
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Note 1: Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability.
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AN_SY8081
Typical Performance Characteristics
Efficiency vs. Load Current
95 95
Efficiency vs. Load Current
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90
90
85 85 80 80 75 75 VIN=3.3V,VOUT=1.2V VIN=4.2V,VOUT=1.2V VIN=5V,VOUT=1.2V VIN=3.3V,VOUT=1.8V VIN=4.2V,VOUT=1.8V VIN=5V,VOUT=1.8V
70 0.1 1 10 0.001 0.01
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0.1 VOUT(AC) VLX IL VOUT(AC) VLX IL
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1 10 1A/div
Load Current (A)
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10
Efficiency vs. Load Current
100
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Load Current (A)
Output Ripple
(VIN=5.0V,VOUT=1.8V, ILOAD=0A)
50mV/div
95
90
5V/div
85
80
VIN=4.2V,VOUT=3.3V VIN=5V,VOUT=3.3V
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0.2A/div
75 0.001
0.01
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0.1 1
Load Current (A)
Time (2ms/div)
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Output Ripple
(VIN=5.0V,VOUT=1.8V, ILOAD=1.0A) 50mV/div
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5V/div
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Time (200ns/div)
AN_SY8081 Rev. 0.9
Silergy Corp. Confidential- Prepared for Customer Use Only
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AN_SY8081
Startup
(VIN=5.0V, VOUT=1.8V, ILOAD=1A) EN 2V/div
Shutdown
(VIN=5.0V, VOUT=1.8V, ILOAD=1A)
EN
2V/div
VOUT
1V/div
VOUT VLX
1V/div 5V/div
VLX
5V/div
IL IL 1A/div
1A/div
Time (1ms/div)
Short Circuit Protection
(VIN=5.0V, VOUT=1.8V, 1A to Short)
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VOUT 1V/div IL 1A/div
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Load Transient
(VIN=5.0V, VOUT=1.8V, ILOAD=0.1-1.0A)
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AN_SY8081 Rev. 0.9
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VOUT(AC)
IL
Time (40µs/div)
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200mV/div
0.5A/div
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Time (1ms/div)
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Time (20µs/div)
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