Basis Thermal Design family device, 3-terminal regulator, easily

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Basis Thermal Design family device, 3-terminal regulator, easily

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AN008
Basis Thermal Design
family device, 3-terminal regulator, easily used with protection features that expected high performance voltage regulation application. These devices provide short-circuit protection, thermal shutdown protection internal current limit protection against overload condition that would create over heating junction temperature.
Upper: output voltage (1V/DIV) Lower: output current (2A/DIV)
Protection Diodes
During normal operation, device needs protection diode. internal diode between input output pins handle microsecond surge current. Even with large output capacitance, very difficult those values surge current normal operation. damage will occur, unless high value output capacitors input shorted ground instantaneously. crowbar circuit input device generate those kinds current diode from output-to-input then recommended. Normal power supply cycling even plugging unplugging system will generate sufficient large current damage device (see Figure
AIC1086 Topology Function block diagram
(1)Current Limit Protection
Like other power regulation family safety protection area. current limit protection works while outputting heavy-loading current keeps output current within safe operating scope. output voltage decreases lower voltage level same time. family protection function designed output current limit when over-current happen downstream devices protected from being damaged.
VOUT
COUT
Figure Diagram
AIC1086
Protection
Diodes
Ripple Rejection
Figure AIC1086 Current Limit Test
2000
recommended family
AN008
device application required improving ripple rejection.
Load Regulation
Being three-terminal device, family unable provide true remote load sensing. resistance wire connecting regulator load will limit load regulation. Please refer datasheet detail measurement. Figure When fixed type regulator used, load should connected output terminal positive side ground terminal negative side. output voltage measured following equation:
connecting bypass capacitor from ground reduce output voltage ripple significantly (see Figure3). bypass capacitor prevents output ripple from being amplified output voltage loading current increases. function defined
Here output ripple frequency CADJ bypass capacitor (For figure ripple rejection capability intensifies output capacitor increases, output ripple will then reduced. more information, please refer family datasheet.
Vout (RS1 RS2)
Figure When adjustable type regulator used, load should connected output terminal positive side ground terminal negative side. output voltage measured following equation:
Function block diagram CADJ
AIC1086 Topology VOUT
VREF
(RS1 RS2)
COUT
Load regulation circuit' ability maintain specified output voltage level under different load conditions, which defined
Figure (CADJ)
Ripple Rejection (dB) (AIC1722D
AIC1086
Bypass Capacitor
VOUT
Figure shows PMOS voltage regulator. ratio output voltage variation given load current variation (VOUT/I) under constant input voltage calculated follow. Here, series pass element, current gain transconductance error amplifier operating point.
COUT=10µF, IL=1Ma COUT=1µF, IL=1mA COUT=1µF, IL=40mA VIN=5V 1Vp-p
Frequency (KHz)
Figure 1722D-33 Frequency Ripple Rejection
Assume that there small output current change (I), change output current causes output voltage change calculated
Vout IoREQ(REQ
AN008
Where equivalent output resistor .The change sensed voltage multiplied error amplifier input difference PMOS current gain (Figure7) must large enough achieve specified change output current. Thus,
VOUT
ERROR AMP.
)VOUT
Figure
Reference
PMOS Voltage Regulator
Then, load regulator obtained from above equation.
VOUT
Since load regulation steady-state parameter, frequency components neglected. load regulation limited open loop current gain system. noted from above equation, increasing open loop current gain improved load regulation.
Quiescent Current Ground Current
Quiescent current ground current difference between input output current family. Minimum quiescent current necessary maximize current efficiency. defined:
Quiescent current consists bias current drive current series pass element, which does contribute output power. series pass element, function diagram, ambient temperature, etc, determine value quiescent current. Linear dropout voltage usually employ bipolar transistors series pass elements. Figure :The collector current bipolar transistors defined Where collector current bipolar transistor, common-emitter current gain bipolar transistor base current bipolar transistor. base current bipolar transistor proportional collector current. When output current increases, base current increases, too. Since base current contributes quiescent current, bipolar transistors have higher quiescent current than transistors. same time, during dropout region quiescent current will increase, because additional parasitic current path between emitter base bipolar transistors, which caused lower base voltage than that output voltage.
VOUT
VOUT
Figure Fixed Regulator
VOUT
VOUT
Figure Adjustable Regulator
AN008
Figure drain source current transistors defined
Figure figure show ground current with respect input voltage temperature.
Ground Current Input Voltage
K(VGS )(VDS K(VDS VT)2
Ground Current (µA)
transistor conductivity parameter gate source voltage threshold voltage drain current function gate source voltage, gate current.
Input Voltage
Figure AIC1722 Input Current Characteristics
Ground Current Temperature
Ground
Figure Transistors
Characteristics Bipolar
Ground Current (µA)
VGS4 VGS3 VGS2 VGS1
=300mA =150mA
IL=0.1mA
Temperature (°C)
Figure Characteristic Transistors Figure 1722 Temperature Ground Current Characteristics bipolar transistors, quiescent current increases proportionally with output current because series pass element current-driven device. transistors, quiescent current near constant value with respect load current since device voltage-driven. only things that contribute quiescent current transistors biasing currents band-gap, sampling resistor, error amplifier. most applications where power consumption critical where small bias current requested comparison with output current, voltage regulator using transistors essential choice.
Thermal Considerations
family internal power thermal-limiting circuitry, which designed protect device against overload conditions. continuous normal load conditions, however, maximum ratings junction temperature must exceeded. important more attention sources thermal resistance from junction ambient This includes junction-to-case, case-to-heat sink interface, heat sink resistance itself.
AN008
take following condition example 1086. (max continuous)=5V, VOUT=3.3V, IOUT=1A HEAT package with thermal compound. TO-220 regulator, dropout voltage quiescent current must reduced. addition, dropout voltage between input output must minimized since power dissipation regulators affects efficiency significantly. Power dissipation example AIC1722: Input voltage Output voltage 3.3V Output current 300mA Power dissipation under these conditions calculated: PD=(VIN-VOUT)(IOUT)=1.7W Junction temperature will equal TJ=TA+PD(HEAT SINK CASE-TO-HEAT SINK operating junction temperature range: (Operating Junction Temperature Range) Ground (max) current 80µA
300mA 100% (300mA 88µ8
Layout Note
According following parameter, achieve maximum allowable Temperature Rise, (TR) (max)- (max) where (max) maximum allowable junction temperature (max) maximum ambient temperature suitable application. calculated values maximum allowable value junction-to-ambient thermal resistance (JA) calculated: JA=TR/PD
storage temperature range: +1.7W (Storage Temperature Range) above cases, junction temperature lower than maximum rating, this ensure reliable operation.
Efficiency
quiescent ground current input/output voltage with respect efficiency regulator input/output voltage with following equation:
maximum allowable value achieved SOT-223 package TO-220 package TO-263 package, heatsink needed since package will dissipate heat satisfy these requirements. calculated value falls below these limits, extra heatsink device required. TABLE Different Heatsink Area Table shows values SOT-223 TO-263 different heatsink area.
order achieve higher efficiency
AN008
copper patterns that used measure these shown below. Copper Area Layout Side 0.012 0.064 0.52 0.75 0.065 0.174 0.283 0.391
Bottom Side 0.065 0.174 0.283 0.391
Thermal Resistance °C/W) °C/W) TO-263 SOT-223
TABLE Series Temperature table temperature rise these operation conditions recommended. Test TYPEAIC1722-33CZL(TO-92) without heat sink Power Long time test: 0.5W 0.7W(-) dissipation Test time: 20min. Load current 298mA 417mA load: Input voltage: 5VDC Output voltage 3.302V 3.307V Output Package voltage :3.322VDC Test TYPEAIC1722-33CZL(SOT-89)IC stick Power Long time test 0.5W 0.6W(-) dissipation Test time: 20min. Load current 290mA 348mA load: Input voltage: 5VDC Output voltage 3.305V 3.299V Output Package voltage:3.278VDC
AN008
Test TYPEAIC1723-33CE(TO-252)IC stick Power Long time test 0.5W 0.9W dissipation Test time: 20min. Load current 300mA 538mA load Input voltage: 5VDC Output voltage 3.321V 3.313V Output Package voltage:3.328VDC Test TYPEAIC1723-33CF(TO-251) without heat sink Power 0.9W Dissipation Long time test Load Current 524mA 582mA Test time: 20min. load: Output Voltage 3.294V 3.295V Input voltage: 5VDC Output Package voltage:3.284VDC Junction Test TYPEAIC1084CT(TO-220) without heat sink Power 3W(-) Long time test Dissipation Load Current 600mA 1.802A Test time: 20min. load: Output Voltage 3.331V 3.311V Input voltage: 5VDC Output Package voltage:3.335VDC Junction Test TYPEAIC1084CT(TO-220) with heat sink Power Long time test Dissipation Test time: 20min. Load Current 600mA 1.802A load: Output Voltage 3.333V 3.322V Input voltage: 5VDC Output Package voltage:3.335VDC Junction Test TYPEAIC1084CT(TO-220) stick Power Long time test Dissipation Test time: 20min. Load Current 600mA 1.802A load: Output Voltage 3.333V 3.324V Input voltage: 5VDC Output Package voltage:3.335VDC Junction
1W(-) 598mA 3.316V
1.1W(-) 641mA 3.296V
6W(-) 3.604A 3.291V
6W(-) 3.604A 3.219V 6W(-) 3.604A 3.197V
AN008
Test TYPEAIC1084CM(TO-263) stick Power 6W(-) Long time test Dissipation Load Current 594mA 1.784A 3.567A Test time: 20min. load: Output Voltage 3.314V 3.296V 3.242V Input voltage 5VDC Package Output voltage:3.318VDC Junction Test TYPEAIC1085CT(TO-220) without heat sink Power 3W(-) Long time test Dissipation Load Current 556mA 1.667A Test time: 20min. load: Output Voltage 3.193V 3.173V Input voltage: 5VDC Output Package voltage:3.200VDC Junction Test TYPEAIC1085CT(TO-220) with heat sink Power Dissipation Load Current Output Voltage Package Junction 556mA 3.192V 1.667A 3.179V
7W(-) 4.162A 3.077V
6W(-) 3.333A 3.285V
Long time test Test time: 20min. load: Input voltage: 5VDC Output voltage:3.200VDC
6W(-) 3.333A 3.176V
Test TYPEAIC1085CT(TO-220) stick Power Long time test Dissipation Load Current 556mA 1.667A Test time: 20min. load: Output Voltage 3.199V 3.192V Input voltage: 5VDC Package Output voltage:3.200VDC Junction Test TYPEAIC1085CM(TO-263) stick Power Long time test Dissipation Load Current 595mA 1.788A Test time: 20min. load: Output Voltage 3.321V 3.310V Input voltage: 5VDC Output Package voltage:3.322VDC Junction
6W(-) 3.333A 3.174V 6W(-) 3.576A 3.192V
AN008
Test TYPEAIC1117CE(TO-252) stick Power Long time test 1.5W Dissipation Load Current 561mA 841mA Test time: 20min. load: Output Voltage 3.204V 3.192V Input voltage 5VDC Output Package voltage:3.217VDC Junction
2W(-) 1.122A 3.184V
Summary
Install 10µF greater) capacitor required between family device' output ground pins reason stability. Without this capacitor, part will oscillate. Even though most types capacitor work, equivalent series resistance (ESR) should held less, aluminum electrolytic type used. Many Aluminum electrolytic capacitors have electrolytes that will freeze under -30°C, solid tantalums recommended operation below -25°C. value this capacitor increased without limit. 10µF greater) capacitor should placed from family input ground lead inductance between input power source exceeds 500nH (approximately inches trace).

Basis Thermal Design family device, 3-terminal regulator, easily

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