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| CS8321 CS8321 Micropower 5V, 150mA Low Dropout Linear Regulator Description The CS8321 is a precision 5V micropower voltage regulator with very low quiescent current (140A typ at 1mA load). The 5V output is accurate within 2% and supplies 150mA of load current with a typical dropout voltage of only 300mV. This combination of low quiescent current and outstanding regulator performance makes the CS8321 ideal for any battery operated equipment. The regulator is protected against reverse battery and short circuit conditions. The device can withstand 45V load dump transients making it suitable for use in automotive environments. Features s 5V 2% Output s Low 140A (typ) Quiescent Current s 150mA Output Current Capability s Fault Protection -15V Reverse Voltage Output Current Limit s Low Reverse Current (Output to Input) Absolute Maximum Ratings Transient Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-15V, 45V Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Internally Limited ESD Susceptibility (Human Body Model) . . . . . . . . . . . . . . . . . . . . . . . . . .2kV Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40C to 150C Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-65C to 150C Lead Temperature Soldering Wave Solder (through hole styles only) . . . . . . . .10 sec. max, 260C peak Reflow (SMD styles only) . . . . . . . .60 sec. max above 183C, 230C peak Block Diagram Package Options 3L TO-220 VIN QP Current Source (Circuit Bias) VOUT 1. VIN 2. Gnd 3. VOUT R QN Current Limit Sense 1 VOUTSense* 3L D2PAK 1. VIN 2. Gnd 3. VOUT + - Error Amplifier R1 Bandgap Reference 1 R2 Gnd *Note: Lead shorted to VOUT in 3 pin applications Other Packages: 16L SO, 16L PDIP, 8L SO, 8L PDIP, (consult factory) Cherry Semiconductor Corporation 2000 South County Trail, East Greenwich, RI 02818 Tel: (401)885-3600 Fax: (401)885-5786 Email: info@cherry-semi.com Web Site: www.cherry-semi.com Rev. 11/25/96 1 A Company CS8321 Electrical Characteristics: 6V < VIN < 26V, IOUT=1mA, -40C TA 125C, -40C TJ 150C unless otherwise specified. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT s Output Stage Output Voltage, VOUT Dropout Voltage (VIN-VOUT) Quiescent Current, (IQ) 9V < VIN < 16V, 100A IOUT 150mA IOUT = 150mA, -40C TA 85C IOUT = 150mA, TA = 125C IOUT = 1mA @ VIN = 13V IOUT < 50mA @ VIN = 13V IOUT < 150mA @ VIN = 13V Load Regulation Line Regulation Ripple Rejection Current Limit Short Circuit Output Current Reverse Current VOUT = 0V VOUT = 5V, VIN = 0V VIN = 14V, 100A < IOUT < 150mA 6V < V < 26V, IOUT = 1mA 7 VIN 17V, IOUT = 150mA, f = 120Hz 60 175 60 4 15 5 5 75 250 200 140 200 4.90 5.00 0.3 5.10 0.5 0.6 200 6 25 50 50 V V V A mA mA mV mV dB mA mA A Package Lead Description PACKAGE LEAD # LEAD SYMBOL FUNCTION 3L D2PAK 1 2 3 3L TO-220 1 2 3 VIN Gnd VOUT Input Voltage Ground. All Gnd leads must be connected to Ground. 5V, 2%, 150mA Output. Circuit Description and Application Notes Voltage Reference and Output Circuitry The CS8321 is a series pass voltage regulator. It consists of an error amplifier, bandgap voltage reference, PNP pass transistor with antisaturation control, and current limit. As the voltage at the input, VIN, is increased, QN is forward biased via R. QN provides base drive for QP. As QP becomes forward biased, the output voltage, VOUT, begins to rise as QPOs output current charges the output capacitor. Once VOUT rises to a certain level, the error amplifier becomes biased and provides the appropriate amount of base current to QP. The error amplifier monitors the scaled output voltage via an internal voltage divider, R1 and R2, and compares it to the bandgap voltage reference. The error amplifierOs output is a current which is equal to the error amplifierOs differential input voltage times its transconductance. Therefore, the error amplifier varies the base drive current to QN, which provides bias to QP, based on the difference between the reference voltage and the scaled output voltage, VOUT. Antisaturation Protection An antisaturation control circuit has also been added to prevent the pass transistor from going into deep saturation, which would cause excessive power dissipation due to large bias currents lost to the substrate via a parasitic PNP transistor, as shown in Figure 1. VIN QP QParasitic Substrate Figure 1. The parasitic PNP transistor which is part of the pass transistor (QP) structure. VOUT 2 CS8321 Circuit Description and Application Notes: continued Current Limit Limit The output stage is protected against short circuit conditions. As shown in Figure 2, the output current will fold back when the faulted load is continually increased. This technique has been incorporated to limit the total power dissipation across the device during a short circuit condition, since the device does not contain overtemperature shutdown. ity. The aluminum electrolytic capacitor is the least expensive solution, but, if the circuit operates at low temperatures (-25C to -40C), both the value and ESR of the capacitor will vary considerably. The capacitor manufacturers data sheet usually provides this information. The value for the output capacitor COUT shown in Figure 3 should work for most applications, however it is not necessarily the best solution. To determine an acceptable value for COUT for a particular application, start with a tantalum capacitor of the recommended value and work towards a less expensive alternative part. Step 1: Place the completed circuit with a tantalum capacitor of the recommended value in an environmental chamber at the lowest specified operating temperature and monitor the outputs with an oscilloscope. A decade box connected in series with the capacitor will simulate the higher ESR of an aluminum capacitor. Leave the decade box outside the chamber, the small resistance added by the longer leads is negligible. Step 2: With the input voltage at its maximum value, increase the load current slowly from zero to full load while observing the output for any oscillations. If no oscillations are observed, the capacitor is large enough to ensure a stable design under steady state conditions. Step 3: Increase the ESR of the capacitor from zero using the decade box and vary the load current until oscillations appear. Record the values of load current and ESR that cause the greatest oscillation. This represents the worst case load conditions for the regulator at low temperature. Step 4: Maintain the worst case load conditions set in step 3 and vary the input voltage until the oscillations increase. This point represents the worst case input voltage conditions. Step 5: If the capacitor is adequate, repeat steps 3 and 4 with the next smaller valued capacitor. A smaller capacitor will usually cost less and occupy less board space. If the output oscillates within the range of expected operating conditions, repeat steps 3 and 4 with the next larger standard capacitor value. Step 6: Test the load transient response by switching in various loads at several frequencies to simulate its real working environment. Vary the ESR to reduce ringing. Step 7: Remove the unit from the environmental chamber and heat the IC with a heat gun. Vary the load current as instructed in step 5 to test for any oscillations. Once the minimum capacitor value with the maximum ESR is found, a safety factor should be added to allow for the tolerance of the capacitor and any variations in regulator performance. Most good quality aluminum electrolytic capacitors have a tolerance of 20% so the minimum value found should be increased by at least 50% to allow for this tolerance plus the variation which will occur at low temperatures. The ESR of the capacitor should be less than 50% of the maximum allowable ESR found in step 3 above. 0.34257 0.30831 0.27405 0.23980 Load Current 0.20554 0.17128 0.13703 0.10277 0.06851 * Curve will vary with temperature and process variation. 0.03426 0.00000 0.00 0.51 1.02 1.52 2.03 2.54 3.05 3.56 4.06 4.57 5.08 Output Voltage Figure 2. Typical current limit and fold back waveform. Stability Considerations The output or compensation capacitor helps determine three main characteristics of a linear regulator: start-up delay, load transient response and loop stability. VIN CIN* 0.1mF VOUT COUT** CS8321 VOUTSense*** 10mF * CIN required if regulator is located far from the power supply filter. ** COUT required for stability. Capacitor must operate at minimum temperature expected. *** Pin internally shorted to VOUT in 3 pin applications. Figure 3: Test and application circuit showing output compensation. The capacitor value and type should be based on cost, availability, size and temperature constraints. A tantalum or aluminum electrolytic capacitor is best, since a film or ceramic capacitor with almost zero ESR can cause instabil- 3 CS8321 Circuit Description and Application Notes: continued Calculating Power Dissipation in a Single Output Linear Regulator The maximum power dissipation for a single output regulator (Figure 3) is: PD(max)=(VIN(max)VOUT(min))IOUT(max)+VIN(max)IQ (1) Heatsinks A heatsink effectively increases the surface area of the package to improve the flow of heat away from the IC and into the surrounding air. Each material in the heat flow path between the IC and the outside environment will have a thermal resistance. Like series electrical resistances, these resistances are summed to determine the value of RQJA: RQJA = RQJC + RQCS + RQSA where: RQJC = the junctiontocase thermal resistance, RQCS = the casetoheatsink thermal resistance, and RQSA = the heatsinktoambient thermal resistance. RQJC appears in the package section of the data sheet. Like RQJA, it too is a function of package type. RQCS and RQSA are functions of the package type, heatsink and the interface between them. These values appear in heatsink data sheets of heatsink manufacturers. (3) where: VIN(max) is the maximum input voltage, VOUT(min) is the minimum output voltage, IOUT(max) is the maximum output current for the application, and IQ is the quiescent current the regulator consumes at IOUT(max). Once the value of PD(max) is known, the maximum permissible value of RQJA can be calculated: RQJA = 150C - TA PD (2) The value of RQJA can then be compared with those in the package section of the data sheet. Those packages with RQJA's less than the calculated value in equation 2 will keep the die temperature below 150C. In some cases, none of the packages will be sufficient to dissipate the heat generated by the IC, and an external heatsink will be required. IIN VIN IOUT VOUT CS8321 IQ Figure 4: Single output regulator with key performance parameters labeled. 4 CS8321 Package Specification PACKAGE DIMENSIONS IN mm(INCHES) PACKAGE THERMAL DATA Thermal Data RQJC typ RQJA typ 3L TO-220 3.5 50 3L D2PAK 1.0* 10 - 50** uC/W uC/W *Depending on die area **Depending on thermal properties of substrate. RQJA = RQJC + RQCA 3 Lead TO-220 (T) Straight 10.54 (.415) 9.78 (.385) 2.87 (.113) 2.62 (.103) 3.96 (.156) 3.71 (.146) 4.83 (.190) 4.06 (.160) 1.40 (.055) 1.14 (.045) 6.55 (.258) 5.94 (.234) 14.99 (.590) 14.22 (.560) 1.52 (.060) 1.14 (.045) 14.22 (.560) 13.72 (.540) 1.40 (.055) 1.14 (.045) 6.17 (.243) REF 1.02 (.040) 0.63 (.025) 2.79 (.110) 2.29 (.090) 5.33 (.210) 4.83 (.190) 0.56 (.022) 0.38 (.014) 2.92 (.115) 2.29 (.090) 5 CS8321 Package Specification: continued 3 Lead D2PAK (DP) 10.31 (.406) 10.05 (.396) 1.68 (.066) 1.40 (.055) 1.40 (.055) 1.14 (.045) 8.53 (.336) 8.28 (.326) 15.75 (.620) 14.73 (.580) 2.74(.108) 2.49(.098) 1.40 (.055) 1.14 (.045) 0.91 (.036) 0.66 (.026) 2.54 (.100) REF .254 (.010) REF 2.79 (.110) 2.29 (.090) 4.57 (.180) 4.31 (.170) 0.10 (.004) 0.00 (.000) Ordering Information Part Number CS8321YT3 CS8321YDP3 CS8321YDPR3 Rev. 11/25/96 Description 3L TO-220 Straight 3L D2PAK 3L D2PAK (tape & reel) Cherry Semiconductor Corporation reserves the right to make changes to the specifications without notice. Please contact Cherry Semiconductor Corporation for the latest available information. 6 (c) 1999 Cherry Semiconductor Corporation |
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