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2022-09-23 11:12:17
Fan 1589 VRM8.5 2.7A, 1.2V Low Dropout Linear Regulator
feature
Nearly Transient Response Low Dropout Load Regulation up to 2.7A: Typical 0.05% Trim Current Limit On-Chip Thermal Limit Standard TO-220 , TO-263, TO-263 Heart Cut and TO-252 (DPAK) Packages
application
GTL+ Bus Power Low Voltage Logic Power Switching Power Supply Post Regulator for VRM 8.5
illustrate
The FAN1589 is a low dropout three terminal regulator with 2.7A output current capability. This device is optimized for VTT bus termination, where transient response and minimum input voltage are critical. The FAN1589 provides 1.2V and 2.7A current capability termination with fixed GTL+ bus VTT. The current limit is trimmed to ensure the specified output current and to control the short circuit current. On-chip thermal limiting protects against overload and ambient temperatures that can cause over-connection. The FAN1589 complies with industry standard TO-220, TO-263, TO-263 mid-cut and TO-252 (DPAK) power packs.
Electrical Characteristics Tj=25°C unless otherwise specified. Indicates the specification applicable to the specified operating temperature range.
notes:
1. See Thermal Regulation Specifications for output voltage changes due to heating effects. Load and line regulation are measured at constant junction temperature with low duty cycle pulse tests.
2. Line and load regulation guarantees maximum power dissipation (W). Power dissipation is determined by input to output differential and output current. Guaranteed maximum output power will not be available over the full input/output voltage range
Application Information General: FAN1589 is a three-terminal regulator for GTL+VTT terminal applications. It is short-circuit protected and provides thermal shutdown to shut down the regulator when the junction temperature exceeds about 150°C. The FAN1589 provides low voltage drop and fast transient response. Frequency compensation is used low while remaining stable. This is critical to meet the needs of low voltage high speed microprocessor busses like GTL+. The stability fan 1589 requires an output capacitor for frequency compensation. It is recommended to use 22μF solid tantalum or 100μF aluminum electrolysis to ensure the stability of the output. Their frequency compensation devices optimize frequency response capacitors with low ESR. Generally speaking, it is recommended to use capacitors with ESR less than 1Ω. The fan 1589 does not need any protection diodes when the protection diodes are working properly. Protection diodes are usually not required between the input and output pins. Internal diodes between the input and output pins of the fan 1589 can handle microsecond surge currents of 50A to 100A. Even with large output capacitors it is difficult to obtain these inrush current values during normal operation. Only large output value capacitors, such as 1000µF to 5000µF pins, can be damaged by a momentary short circuit to ground. A crowbar circuit at the input can generate these levels of current; then it is recommended to use diodes from the output to the input as shown. Normally, normal power cycling or system "hot swapping" will not draw enough current to cause any damage. As with any IC regulator, exceeding the maximum input voltage differential will cause the internal transistors to fail without any protection circuit functionality.
Load regulation cannot provide true remote sensing load because the FAN1589 is a three terminal device. Load regulation is limited by the resistance of the wires connecting the regulator to the load. Load regulation is measured at the bottom of the package according to the data sheet specification. For fixed voltage devices, the negative side sensing is the correct Kelvin connection to the device ground pin back to the negative side of the load. as the picture shows.
The thermal factor fan 1589 protects its own internal power and thermal limiting circuits during overload conditions. However, for normal continuous load conditions, do not exceed the maximum joint temperature rating. It is important to consider the source of thermal resistance from the connection point to the surrounding environment. These sources include the resistance connected to the case, the case-to-heatsink interface resistance, and the heatsink resistance. Thermal resistance specifications have been developed to more accurately reflect device temperatures and ensure safe operating temperatures. For example, using the FAN1589 to generate a 2.7A@3.3V supply (3.2V to 3.6V) voltage is 1.2V±2%.
Suppose:
VIN = 3.6V worst case
VOUT=1.176V worst case
IOUT=2.7A continuous
TA=70°C•θambient temperature=3°C/W (assuming heat sink and thermally conductive material) The power dissipation in this application is:
PD=(VIN-Voucher)*(input)=(3.6–1.18)*(2.7)=6.53W
From the spec sheet:
TJ = TA + (PD) * (θ case to ambient + θJC) = 70 + (6.53) * (3 + 3) = 109°C junction temperature below maximum rating.
The IC specifies a thermal resistance connected to the case connected to the bottom of the case just below the die. This is the path of least resistance for heat flow. Proper installation ensures that from this area to the radiator. The chassis-to-heatsink interface is recommended for use with thermally conductive materials. Use thermal if the enclosure of the device must be electrically isolated and include resistance to its contribution to the total heat. The housing of the fan 1589 is directly connected to the output of the device.
notes:
1. Dimensions do not include die flash and metal burrs.
2. The distance height from the lead head to the reference plane -B-.
3. Measure foot length (inside R) with lead surface reference datum A.
4. Dimensions do not include dam protrusion or intrusion.
5. The wires formed on the seat are in plane with each other site -C-.