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CS5205A-1
CS5205A-1
5A Adjustable Linear Regulator
Description
The CS5205A-1 linear regulator provides 5A at an adjustable voltage with an accuracy of 1%. Two external resistors are used to set the output voltage within a 1.25V to 13V range. The regulator is intended for use as a post regulator and microprocessor supply. The fast loop response and low dropout voltage make this regulator ideal for applications where low voltage operation and good transient response are important. The circuit is designed to operate with dropout voltages as low as 1V depending on the output current level. The maximum quiescent current is only 10mA at full load. The regulator is fully protected against overload conditions with protection circuitry for Safe Operating Area (SOA), overcurrent and thermal shutdown. The CS5205A-1 is pin compatible with the LT1084 family of linear regulators but has lower dropout voltage. The regulator is available in TO-220 and surface mount D2 packages.
Features
s Output Current to 5A s Output Trimmed to +/- 1% s Dropout Voltage 1.15V @ 5A s Fast Transient Response s Fault Protection Circuitry Thermal Shutdown Overcurrent Protection Safe Area Protection
Block Diagram
Package Options
3L TO-220
Tab (VOUT)
3L D2PAK
V OUT V IN
1
Output Current Limit Thermal Shutdown + Error Amplifier Adj
1 2 3
Adj VOUT VIN
1
Bandgap
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. 7/8/97
1
A
Company
CS5205A-1
Absolute Maximum Ratings Supply Voltage, VCC .....................................................................................................................................................................17V Operating Temperature Range ..................................................................................................................................-40C to 70C Junction Temperature ...............................................................................................................................................................150C Storage Temperature Range .....................................................................................................................................-60C 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 Electrical Characteristics: CIN = 10F, COUT = 22F Tantalum, VIN VOUT=3V, VIN 15V, 0C TA 70C, TJ +150C,
unless otherwise specified, Ifull load = 5A. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
s Adjustable Output Voltage Reference Voltage (Notes 1 and 2) Line Regulation Load Regulation (Notes 1 and 2) Dropout Voltage (Note 3) Current Limit Minimum Load Current Adjust Pin Current Adjust Pin Current Change Thermal Regulation Ripple Rejection Temperature Stability RMS Output Noise Thermal Shutdown Thermal Shutdown Hysteresis 10Hzf10kHz; TA=25C 150 1.5VVINVOUT4V; 10mAIOUT5A 30ms pulse; TA=25C f=120Hz; CAdj=25F; IOUT=5A VINVOUT=1.5V; VAdj = 0V 10mAIOUT5A 1.5VVINVOUT6V; IOUT=10mA VINVOUT=1.5V; 10mAIOUT5A IOUT=5A; TJ 25C VINVOUT=3V; TJ 25C VINVOUT=9V VINVOUT=7V 5.5 1.241 (-1%) 1.254 0.04 0.08 1.15 8.5 1.0 1.2 50 0.2 0.003 82 0.5 0.003 180 25 6 100 5.0 1.266 (+1%) 0.20 0.4 1.25 V % % V A A mA A A %W dB % %VOUT C C
Note 1: Load regulation and output voltage are measured at a constant junction temperature by low duty cycle pulse testing. Changes in output voltage due to thermal gradients or temperature changes must be taken into account separately. Note 2: Specifications apply for an external Kelvin sense connection at a point on the output pin 1/4O from the bottom of the package. Note 3: Dropout voltage is a measurement of the minimum input/output differential at full load.
Package Pin Description
PACKAGE PIN # PIN SYMBOL FUNCTION
D2PAK 1 2 3
3L TO-220 1 2 3
Adj VOUT VIN
Adjust pin (low side of the internal reference). Regulated output voltage (case). Input voltage.
2
CS5205A-1
Typical Performance Characteristics
1.25 1.20 TCASE = 0C
Output Voltage Deviation (%)
0.10 0.08 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 -0.12
1.15
Dropout Voltage (V)
1.10 1.05 1.00 0.95 0.90 0.85 0.80 0.75 0.70
0 1 2 3 Output Current (A) 4 5
TCASE = 125C TCASE = 25C
0
10
20
30
40
50
60
70
80
90 100 110 120 130
TJ (C)
Dropout Voltage vs. Output Current
Reference Voltage vs. Temperature
0.200 0.175
Output Voltage Deviation (%)
2.500
0.150 0.125 0.100
TCASE = 25C
Minimum Load Current (mA)
2.175
1.850
TCASE = 0C
1.525
0.075
TCASE = 125C
1.200 TCASE = 125C 0.875 TCASE = 25C
0.050 0.025
TCASE = 0C
0.000
0 1 2 3 4 5 Output Current (A)
0.550 1 2 3 4 5 VIN - VOUT (V) 6 7 8 9
Load Regulation vs. Output Current
Minimum Load Current
100.0 90.0
Ripple Rejection (dB)
80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0
101 102 103 Frequency (Hz) 104 105
TCASE = 25C IOUT = 5A (VIN VOUT) = 3V VRIPPLE = 1.6VPP CAdj = 25mF
Ripple Rejection vs. Frequency
3
CS5205A-1
Applications Information The CS5205A-1 linear regulator provides an adjustable voltage at currents up to 5A. The regulator is protected against short circuit, and include thermal shutdown and safe area protection (SOA) circuitry. The SOA protection circuitry decreases the maximum available output current as the input-output differential voltage increases. The CS5205A-1 has a composite PNP-NPN output transistor and requires an output capacitor for stability. A detailed procedure for selecting this capacitor is included in the Stability Considerations section.
Adjustable Operation
The adjustable regulator (CS5205A-1) has an output voltage range of 1.25V to 13V. An external resistor divider sets the output voltage as shown in Figure 1. The regulator maintains a fixed 1.25V (typical) reference between the output pin and the adjust pin. A resistor divider network R1 and R2 causes a fixed current to flow to ground. This current creates a voltage across R2 that adds to the 1.25V across R1 and sets the overall output voltage. The adjust pin current (typically 50A) also flows through R2 and adds a small error that should be taken into account if precise adjustment of VOUT is necessary. The output voltage is set according to the formula: VOUT = VREF R1 + R2 + IAdj R2 R1
tor with almost zero ESR, can cause instability. The aluminum electrolytic capacitor is the least expensive solution. However, when the circuit operates at low temperatures, both the value and ESR of the capacitor will vary considerably. The capacitor manufacturers data sheet provides this information. A 22F tantalum capacitor will work for most applications, but with high current regulators such as the CS5205A-1 the transient response and stability improve with higher values of capacitor. The majority of applications for this regulator involve large changes in load current so the output capacitor must supply the instantaneous load current. The ESR of the output capacitor causes an immediate drop in output voltage given by: AEV = AEI ESR For microprocessor applications it is customary to use an output capacitor network consisting of several tantalum and ceramic capacitors in parallel. This reduces the overall ESR and reduces the instantaneous output voltage drop under load transient conditions. The output capacitor network should be as close as possible to the load for the best results.
Protection Diodes
(
)
The term IAdj R2 represents the error added by the adjust pin current. R1 is chosen so that the minimum load current is at least 10mA. R1 and R2 should be the same type, e.g. metal film for best tracking over temperature. The adjust pin is bypassed to improve the transient response and ripple rejection of the regulator.
When large external capacitors are used with a linear regulator it is sometimes necessary to add protection diodes. If the input voltage of the regulator gets shorted, the output capacitor will discharge into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage and the rate at which VIN drops. In the CS5205A-1 linear regulator, the discharge path is through a large junction and protection diodes are not usually needed. If the regulator is used with large values of output capacitance and the input voltage is instantaneously shorted to ground, damage can occur. In this case, a diode connected as shown in Figure2 is recommended.
VIN C1
VIN
VOUT
VOUT VIN VREF R1 C2 C1 VIN
IN4002
(optional) VOUT VOUT
CS5205A-1
Adj
CS5205A-1
R1 Adj C2
IAdj CAdj R2 CAdj R2
Figure 1. Resistor divider scheme for the adjustable version.
Figure 2. Protection diode scheme for adjustable output regulator.
Stability Considerations
Output Voltage Sensing
The output or compensation capacitor helps determine three main characteristics of a linear regulator: start-up delay, load transient response and loop stability. The capacitor value and type is based on cost, availability, size and temperature constraints. A tantalum or aluminum electrolytic capacitor is best, since a film or ceramic capaci4
Since the CS5205A-1 is a three terminal regulator, it is not possible to provide true remote load sensing. Load regulation is limited by the resistance of the conductors connecting the regulator to the load.
CS5205A-1
Applications Information: continued Best load regulation occurs when R1 is connected directly to the output pin of the regulator as shown in Figure 3. If R1 is connected to the load, RC is multiplied by the divider ratio and the effective resistance between the regulator and the load becomes RC R1 + R2 R1 The maximum power dissipation for a regulator is: PD(max)={VIN(max)VOUT(min)}IOUT(max)+VIN(max)IQ 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 IQ is the maximum quiescent current at IOUT(max). A heat sink effectively increases the surface area of the package to improve the flow of heat away from the IC and into the surrounding air.
VIN VOUT RC conductor parasitic resistance
(2)
(
)
RC = conductor parasitic resistance
CS5205A-1
R1 Adj
RLOAD
Each material in the heat flow path between the IC and the outside environment has a thermal resistance. Like series electrical resistances, these resistances are summed to determine RQJA, the total thermal resistance between the junction and the surrounding air. 1. Thermal Resistance of the junction to case, RQJC (C/W) 2. Thermal Resistance of the case to Heat Sink, RQCS (C/W)
R2
3. Thermal Resistance of the Heat Sink to the ambient air, RQSA (C/W) These are connected by the equation:
Figure 3. Grounding scheme for the adjustable output regulator to minimize parasitics.
RQJA = RQJC + RQCS + RQSA
(3)
The value for RQJA is calculated using equation (3) and the result can be substituted in equation (1). The value for RQJC is normally quoted as a single figure for a given package type based on an average die size. For a high current regulator such as the CS5205A-1 the majority of the heat is generated in the power transistor section. The value for RQSA depends on the heat sink type, while RQCS depends on factors such as package type, heat sink interface (is an insulator and thermal grease used?), and the contact area between the heat sink and the package. Once these calculations are complete, the maximum permissible value of RQJA can be calculated and the proper heat sink selected. For further discussion on heat sink selection, see application note OThermal Management for Linear Regulators.O
Calculating Power Dissipation and Heat Sink Requirements
The CS5205A-1 linear regulator includes thermal shutdown and safe operating area circuitry to protect the device. High power regulators such as these usually operate at high junction temperatures so it is important to calculate the power dissipation and junction temperatures accurately to ensure that an adequate heat sink is used. The case is connected to VOUT on the CS5205A-1, electrical isolation may be required for some applications. Thermal compound should always be used with high current regulators such as these. The thermal characteristics of an IC depend on the following four factors: 1. Maximum Ambient Temperature TA (C) 2. Power dissipation PD (Watts) 3. Maximum junction temperature TJ (C) 4. Thermal resistance junction to ambient RQJA (C/W) These four are related by the equation TJ = TA + PD RQJA (1)
The maximum ambient temperature and the power dissipation are determined by the design while the maximum junction temperature and the thermal resistance depend on the manufacturer and the package type.
5
CS5205A-1
Package Specification
PACKAGE DIMENSIONS IN mm(INCHES) PACKAGE THERMAL DATA
Thermal Data RQJC RQJA typ typ
3L TO-220 1.6 50
3L D2PAK 1.6 10 - 50*
uC/W uC/W
*Depending on thermal properties of substrate. RQJA = RQJC + RQCA
3 Lead TO-220 (T) Straight 3 Lead D2PAK (DP)
10.31 (.406) 10.05 (.396) 1.40 (.055) 1.14 (.045) 20 typ 1.88 (.066) 1.40 (.055) 6 4
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)
8.53 (.336) 8.28 (.326)
14.99 (.590) 14.22 (.560)
B 15.75 (.620) 14.73 (.580) EPIN 6 4 1.40 (.055) 1.14 (.045) 0.91 (.036) 0.66 (.026) 2.54 (.100) REF A 3 0 6 4 (Both Sides) B 2.74(.108) 2.49(.098) 0.10(.004) 0.00(.000) 2.79 (.110) 2.29 (.090)
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)
4.57 (.180) 4.31 (.170) C
Ordering Information
Part Number Type CS5205A-1GT3 5A, adj. output CS5205A-1GDP3 5A, adj. output CS5205A-1GDPR3 5A, adj. output
Description 3L TO-220 Straight 3L D2PAK 3L D2PAK (tape & reel) 6
Cherry Semiconductor Corporation reserves the right to make changes to the specifications without notice. Please contact Cherry Semiconductor Corporation for the latest available information.
(c) 1999 Cherry Semiconductor Corporation
Rev. 7/8/97

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