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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
FEATURES
Output voltage: 3.3V, 5V, 12V and adjustable output version Adjustable version output voltage range, 1.23V to 18V 4% 150KHz 15% fixed switching frequency Voltage mode non-synchronous PWM control Thermal-shutdown and current-limit protection ON/OFF shutdown control input Operating voltage can be up to 22V Output load current: 2A SOP8L packages Low power standby mode Built-in switching transistor on chip
GENERAL DESCRIPTION
The FSP3125 series are monolithic IC designed for a
Typical Application
Simple High-efficiency step-down regulator On-card switching regulators Positive to negative converter
step-down DC/DC converter, and own the ability of driving a 2A load without additional transistor. It saves board space. The external shutdown function can be controlled by logic level and then come into standby mode. The internal compensation makes feedback control having good line and load regulation without external design. Regarding protected function, thermal shutdown is to prevent over temperature operating from damage, and current limit is against over current operating of the output switch. If current limit function occurs and FB is down below 0.5V, the switching frequency will be reduced. The FSP3125 series operates at a switching frequency of 150KHz thus allow smaller sized filter components than what would be needed with lower frequency switching regulators. Other features include a guaranteed 4% tolerance on output voltage under specified input voltage and output load conditions, and 15% on the oscillator frequency. The output version included fixed 3.3V, 5V, 12V, and an adjustable type. The chips are available in a standard SOP8L package.
PIN ASSIGNMENT
(Top View)
VIN 1 OUTPUT 2 FB 3
8 GND 7 GND
FSP3125
6 5
GND GND
SD 4
PIN DESCRIPTION
Name VIN OUTPUT FB SD GND GND GND GND No. 1 2 3 4 5 6 7 8 Description Operating Voltage Input Switching Output Output Voltage Feedback Control On/Off Shutdown Ground Ground Ground Ground
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
ABSOLUTE MAXIMUM RATINGS
Parameter Supply Voltage On/Off Pin Input Voltage Feedback Pin Voltage Output Voltage to Ground Power Dissipation Storage Temperature Operating Temperature Operating Voltage Value +24 -0.3 to +18 -0.3 to +18 -1 Internally Limited -65 to +150 -40 to +125 +4.5 to +22 Unit V V V V W V
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, VIN=12V for 3.3V, 5V and adjustable version and VIN=18V for the 12V version. ILOAD = 0.5A) Parameter Feedback Bias Current Oscillator Frequency Short Circuit Oscillator Frequency Saturation Voltage Maximum Duty Cycle(On) Minimum Duty Cycle(Off) Current Limit Output Leakage Current Output=-1 Quiescent Current Output=0 Standby Quiescent Current ON/OFF Pin Logic Input Threshold Voltage ON/OFF Pin Input Current ON/OFF Pin Logic Input Current Thermal Resistance Thermal Resistance with Copper Area of Approximately 3 in2 Symbol IFB Fosc FCSP VSAT DC When Current Limit Occur and VFB 0.5V, TA=25C IOUT= 2A, No Outside Circuit , VFB = 0V force drive on VFB = 0V force drive on VFB =12V force drive off Peak Current No Outside Circuit , VFB = 0V force drive on No Outside Circuit , VFB = 12V force drive off VIN = 22V VFB = 12V force drive off ON/OFF Pin=5V,VIN = 22V Low (Regulator ON) High (Regulator OFF) VLOGIC=0.5V(ON) VLOGIC=2.5V(OFF) SOP8L SOP8L Junction to Case Junction to Ambient 15 70 /W 2.0 Test Conditions VFB = 1.3V (Adjustable Version Only) Min. Typ. -10 127 110 10 150 30 1.25 0 3.6 3.4 6.9 7.5 -50 5 70 1.3 -30 10 200 250 0.6 -5 -15 A A mA mA A V Max. -50 -100 173 173 50 1.4 1.5 100 Unit nA kHz kHz V % A
ICL
IL IQ ISTBY VIL VIH IL IH JC JA
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
ELECTRICAL CHARACTERISTICS(CONTINUED)
(Unless otherwise specified, VIN=12V for 3.3V, 5V and adjustable version and VIN=18V for the 12V version. ILOAD = 0.5A) Parameter Output Feedback Efficiency Output Feedback Efficiency Output Feedback Efficiency Output Feedback FSP3125-5.0V Symbol VFB FSP3125-ADJ VOUT FSP3125-3.3V VOUT FSP3125-12V VOUT Test Conditions 4.5V VIN 22V 0.2A ILOAD 2A VOUT Programmed for 3V VIN =12V, ILOAD= 2A 4.5V VIN 22V 0.2A ILOAD 2A VIN =12V, ILOAD= 2A 7V VIN 22V 0.2A ILOAD 2A VIN =12V, ILOAD= 2A 15V VIN 22V 0.2A ILOAD 2A Min. 1.193 1.18 75 3.168 3.135 78 4.8 4.75 83 11.52 5 5.2 5.25 12.48 3.3 3.432 3.465 Typ. 1.23 Max. 1.267 1.28 Unit V % V % V % V
12
11.4 12.6 Efficiency VIN =15V, ILOAD= 2A 90 Specifications with boldface are for full operating temperature range, the other type are for TJ=25C
%
FUNCTIONAL BLOCK DIAGRAM
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
Function Description
Pin Description +VIN This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be presented at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. Ground Circuit Ground Output Internal Switch. The voltage at this pin switches between (+VIN-VSAT) and approximately -0.5V, with a duty cycle of approximately VOUT/VIN. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be minimized. Feedback Sense the regulated output voltage to complete the feedback loop. SD Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 150uA. Pulling this pin below a threshold voltage of approximately 1.3V turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 18V) shuts the regulator down. If this shutdown feature is not needed, the SD pin can be wired to the ground pin. Thermal Considerations The SOP8L package needs a heat sink under most conditions. The size of the heatsink depends on the input voltage, the output voltage, the load current and the ambient temperature. The FSP3125 junction temperature rises above ambient temperature for a 2A load and different input and output voltages. The data for these curves was taken with the FSP3125(SOP8L package) operating as a buck-switching regulator in an ambient temperature 25 (still air). These temperature increments are all approximate and are affected by many factors. Higher ambient temperatures requires more heat sinker. For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (One exception is the output (switch) pin, which should not have large areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. Package thermal resistance and junction temperature increments are all approximate. The increments are affected by a lot of factors. Some of these factors include board size, shape, thickness, position, location, and even board temperature. Other factors are, trace width, total printed circuit copper area, copper thickness, single or double-sided, multi-layer board and the amount of solder on the board. The effectiveness of the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the board, as well as whether the surrounding air is still or moving. Furthermore, some of these components such as the catch diode will add heat to the PC board and the heat can vary as the input voltage changes. For the inductor, depending on the physical size, type of core material and the DC resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board.
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
Typical Application Circuit
(1) Fixed Output Version Circuit
(2) Adjustable Version Circuit
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
TYPICAL CHARACTERISTICS
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
TYPICAL CHARACTERISTICS(CONTINUED)
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
ORDER INFORMATION
FSP3125XXXX Package: S: SOP8L Temperature Grade: Output Voltage: Packing: Blank: Tube or Bulk E: -40~125 Blank: ADJ A: Tape & Reel 33: 3.3V 50: 5.0V 12: 12V
MARKING INFORMATION
Logo
3125-VV
YYWWXX
Part number: 3125-ADJ: ADJ 3125-33: 3.3V 3125-50: 5.0V 3125-12: 12V Internal code Date code: YY: Year (01=2001) WW: Nth week (01~52)
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150KHZ PWM BUCK DC/DC CONVERTER 2A
FSP3125
PACKAGE INFORMATION
E
H
7(4)
D
7(4) 0.01545 A
e
A1
B
A2
VIEW "A"
Symbol A A1 A2 B C D E e H L
Min. 1.35 0.10 1.35 0.33 0.19 4.80 3.80
Dimensions In Millimeters Nom. Max. 1.60 1.75 0.25 1.45 1.55 0.41 0.51 0.20 0.25 4.90 5.00 3.90 4.00 1.27TYP. 5.80 5.99 6.30 0.38 0.71 1.27 0 8
Dimensions In Inches Min. Nom. 0.053 0.063 0..004 0.053 0.057 0.013 0.016 0.0075 0.008 0.192 0.196 0.148 0.154 0.050TYP. 0.228 0.236 0.015 0.028 0
Max. 0.069 0.010 0.061 0.020 0.010 0.200 0.160 0.248 0.050 8
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