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CS5201-1
CS5201-1
1A Adjustable Linear Regulator
Description
The CS5201-1 linear regulator provides 1A with an output voltage accuracy of 1%. The device uses two external resistors to set the output voltage within a 1.25V to 5.5V range. This 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 less than 1.2V at 1A output current. Device protection includes overcurrent and thermal shutdown. The CS5201 is pin compatible with the LT1086 family of linear regulators. The regulator is available in TO-220, surface mount D2, and SOT-223 packages.
Features
s Output Current to 1A s Output Accuracy to 1% over Temperature s Dropout Voltage (typical) 1.0V @ 1A s Fast Transient Response s Fault Protection Current Limit Thermal Shutdown
Package Options
Application Diagram 3L TO-220
Tab (VOUT)
3L D2PAK
Tab (VOUT)
5V
VIN
VOUT
CS5201-1
Adj 10mF 5V 0.1mF 5V Tant 200W 1% 124W 1%
3.3V @ 1A
1
3L SOT-223
Tab (VOUT)
1
22mF 5V
CS5201 -1 1 Adj 2 VOUT(Tab) 3 VIN
1
Consult factory for fixed output voltage versions.
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. 2/16/98
1
A
Company
CS5201-1
Absolute Maximum Ratings Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7V 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 ESD Damage Threshold (Human Body Model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2kV
Electrical Characteristics: CIN = 10F, COUT = 22F Tantalum, VOUT + VDROPOUT < VIN < 7V, 0C TA 70C, TJ +150C,
unless otherwise specified, Ifull load = 1A. 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 Adjust Pin Current Thermal Regulation (Note 5) Ripple Rejection (Note 5) Thermal Shutdown (Note 6) Thermal Shutdown Hysteresis (Note 6) VINVOUT=1.5V; VAdj = 0V 10mAIOUT1A 1.5VVINVOUT5.75V; IOUT=10mA VINVOUT=1.5V; 10mAIOUT1A IOUT=1A VINVOUT=3V; TJ 25C VINVOUT=3V; IOUT=10mA 30ms pulse; TA=25C f=120Hz; IOUT=1A; VINVOUT=3V; VRIPPLE=1VPP 150 1.1 1.241 (-1%) 1.254 0.02 0.04 1.0 3.1 0.6 50 0.002 80 180 25 210 2.0 100 0.020 1.266 (+1%) 0.20 0.4 1.2 V % % V A mA A %/W dB C C
Minimum Load Current (Note 4) VIN=7V ; VAdj=0
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 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. Note 4: The minimum load current is the minimum current required to maintain regulation. Normally the current in the resistor divider used to set the output voltage is selected to meet the minimum load requirement. Note 5: Guaranteed by design, not 100% tested in production. Note 6: Thermal shutdown is 100% functionally tested in production.
Package Pin Description
PACKAGE PIN # PIN SYMBOL FUNCTION
D2PAK 1 2 3
TO-220 1 2 3
SOT-223 1 2 3 Adj VOUT VIN Adjust pin (low side of the internal reference). Regulated output voltage (case). Input voltage.
2
CS5201-1
Block Diagram
V OUT V IN
Output Current Limit Thermal Shutdown + Error Amplifier
Bandgap Reference Adj
Typical Performance Characteristics
1.00
TCASE
= 0C Output Voltage Deviation (%) 1000
0.10 0.08 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10
0.95 TCASE = 25C 0.90 VDropout (V)
0.85 TCASE = 125C
0.80
0.75 0 200 400 600 IOUT (mA) 800
-0.12 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
0.100
0.65
Output Voltage Deviation (%)
Minimum Load Current (mA)
0.075
0.60 TCASE = 0C 0.55 TCASE = 125C 0.50 TCASE = 25C
0.050
TCASE = 125C TCASE = 25C
0.025
0.45 CIN =COUT =22mF Tantalum 0.40
TCASE = 0C
0.000
0 1 Output Current (A) 2
1
2
3
4 VIN - VOUT (V)
5
6
7
Load Regulation vs. Output Current
Minimum Load Current vs VIN-VOUT
3
CS5201-1
Typical Performance Characteristics: continued
70.0 IO = 10mA Ripple Rejection (dB) 65.0 Adjust Pin Current (mA)
85 75 65 55 45 35 25 15
0 10 20 30 40 50 60 70 80 90 100 110 120 130 101 102 103 104 105 106 Temperature (C)
60.0
55.0
50.0
TCASE = 25C IOUT = 1A (VIN VOUT) = 3V VRIPPLE = 1.0VPP CAdj = 0.1mF
45.0
40.0
Frequency (Hz)
Adjust Pin Current vs. Temperature
Ripple Rejection vs. Frequency
Voltage Deviation (mV)
3.5
200 100 0 -100 -200 VOUT = 3.3V COUT= CIN = 22mF Tantalum CAdj= 0.1mF
3.3 3.1 2.9 2.7 ISC(A)
9 10
2.5 2.3 2.1 1.9 1.7
Load Step (mA)
1000 500 0 0 1 2 3 4 5 Time mS 6 7 8
1.5 1.0 1.5 2.0 2.5 VIN - VOUT (V) 3.0 3.5 4.0
Transient Response
Short Circuit Current vs. VIN - VOUT
Applications Information The CS5201-1 linear regulator provides adjustable voltages at currents up to 1A. The regulator is protected against overcurrent conditions and includes thermal shutdown. The CS5201-1 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
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 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 2mA. R1 and R2 should be the same type, e.g. metal film for best tracking over temperature. While not required, a bypass capacitor from the adjust pin to ground will improve ripple rejection and transient response. A 0.1F tantalum capacitor is recommended for Ofirst cutO design. Type and value may be varied to obtain optimum performance vs. price.
(
)
The CS5201-1 has an output voltage range of 1.25V to 5.5V. 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 4
CS5201-1
Applications Information: continued
EXTERNAL SUPPLY
VIN C1 VIN VOUT VOUT VREF R1 Adj C2
CS5201-1
VIN
IAdj CAdj R2
VOUT VAdj
VOUT
Figure 1. Resistor divider scheme.
Short Circuit Protection
The CS5201-1 linear regulator has an absolute maximum specification of 7V for the voltage difference between VIN and VOUT. However, the IC may be used to regulate voltages in excess of 7V. The main considerations in such a design are power-up and short circuit capability. In most applications, ramp-up of the power supply to VIN is fairly slow, typically on the order of several tens of milliseconds, while the regulator responds in less than one microsecond. In this case, the linear regulator begins charging the load as soon as the VIN to VOUT differential is large enough that the pass transistor conducts current. The load at this point is essentially at ground, and the supply voltage is on the order of several hundred millivolts, with the result that the pass transistor is in dropout. As the supply to VIN increases, the pass transistor will remain in dropout, and current is passed to the load until VOUT reaches the point at which the IC is in regulation. Further increase in the supply voltage brings the pass transistor out of dropout. The result is that the output voltage follows the power supply ramp-up, staying in dropout until the regulation point is reached. In this manner, any output voltage may be regulated. There is no theoretical limit to the regulated voltage as long as the VIN to VOUT differential of 7V is not exceeded. However, the possibility of destroying the IC in a short circuit condition is very real for this type of design. Short circuit conditions will result in the immediate operation of the pass transistor outside of its safe operating area. Overvoltage stresses will then cause destruction of the pass transistor before overcurrent or thermal shutdown circuitry can become active. Additional circuitry may be required to clamp the VIN to VOUT differential to less than 7V if failsafe operation is required. One possible clamp circuit is illustrated in figure 2; however, the design of clamp circuitry must be done on an application by application basis. Care must be taken to ensure the clamp actually protects the design. Components used in the clamp design must be able to withstand the short circuit condition indefinitely while protecting the IC.
Figure 2. Short Circuit Protection Circuit for High Voltage Application.
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. 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 capacitor 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 manufacturersO data sheet provides this information. A 22F tantalum capacitor will work for most applications, but with high current regulators such as the CS5201 the transient response and stability improve with higher values of capacitance. 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
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 CS5201-1 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 Figure 3 is recommended. 5
CS5201-1
Applications Information: continued The thermal characteristics of an IC depend on the following four factors:
VOUT
IN4002 VIN C1 VIN
(optional) VOUT
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
CS5201-1
R1 Adj C2
CAdj
R2
TJ = TA + PD RQJA
(1)
Figure 3. Protection diode for large output capacitors.
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. 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. 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)
RLOAD
Output Voltage Sensing
Since the CS5201-1 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. For the adjustable regulator, the best load regulation occurs when R1 is connected directly to the output pin of the regulator as shown in Figure 4. 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
(2)
(
)
RC conductor parasitic resistance
RC = conductor parasitic resistance
VIN
VIN
VOUT
CS5201-1
R1 Adj
2. Thermal Resistance of the case to Heat Sink, RQCS (C/W) 3. Thermal Resistance of the Heat Sink to the ambient air, RQSA (C/W) These are connected by the equation: RQJA = RQJC + RQCS + RQSA (3)
R2
The value for RQJA is calculated using equation (3) and the result can be substituted in equation (1).
Figure 4. Grounding scheme for the adjustable output regulator to minimize parasitic resistance effects.
Calculating Power Dissipation and Heat Sink Requirements
The CS5201-1 linear regulator includes thermal shutdown and current limit 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 CS5201-1, and electrical isolation may be required for some applications. Thermal compound should always be used with high current regulators such as these. 6
The value for RQJC is 3.5uC/W for a given package type based on an average die size. For a high current regulator such as the CS5201-1 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
CS5201-1
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES) 3 Lead TO-220 (T) Straight PACKAGE THERMAL DATA
Thermal Data RQJC typ RQJA typ
1.40 (.055) 1.14 (.045)
3L TO-220 3.5 50
3L D2PAK 3.5 10 - 50*
3L SOT-223 15 156
uC/W uC/W
*Depending on thermal properties of substrate. RQJA = RQJC + RQCA
10.54 (.415) 9.78 (.385) 2.87 (.113) 2.62 (.103) 3.96 (.156) 3.71 (.146)
4.83 (.190) 4.06 (.160)
6.55 (.258) 5.94 (.234)
14.99 (.590) 14.22 (.560)
3 Lead SOT-223 (ST)
6.70 (.264) 6.30 (.248) 7.30 (.287) 6.70 (.264) 3.15 (.124) 2.95 (.116)
1.52 (.060) 1.14 (.045) 14.22 (.560) 13.72 (.540) 1.40 (.055) 1.14 (.045)
6.17 (.243) REF
3.70 (.146) 3.30 (.130)
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)
1.05 (.041) 0.85 (.033)
2.30 (.090)
1.70 (.067) 1.50 (.060) 0.85 (.033) 0.65 (.026) 4.60 (.181) 1.30 (.051) 1.10 (.043) 10 MAX
0.35 (.014) 0.25 (.010)
0.10 (.004) 0.02 (.001)
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 CS5201-1GT3 CS5201-1GDP3 CS5201-1GDPR3 CS5201-1GST3 CS5201-1GSTR3
Rev. 2/16/98
Type 1A, adj. output 1A, adj. output 1A, adj. output 1A, adj. output 1A, adj. output
Description 3 L TO-220 Straight 3 L D2PAK 3 L D2PAK (tape & reel) 3 L SOT-223 3 L SOT-223 (tape & reel) 7
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

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