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CS8122
CS8122
2% 5V, 750mA Low Dropout Linear Regulator with Delayed RESET
Description
The CS8122 is a precision 5V linear regulator capable of sourcing in excess of 750mA. The RESET Os delay time is externally programmed using a discrete RC network. During power up, or when the output goes out of regulation, the RESET lead remains in the low state for the duration of the delay. This function is independent of the input voltage and will function correctly as long as the output voltage remains at or above 1V. Hysteresis is included in the Delay and the RESET comparators to improve noise immunity. A latching discharge circuit is used to discharge the delay capacitor when it is triggered by a brief fault condition. The regulator is protected against a variety of fault conditions: i.e. reverse battery, overvoltage, short circuit and thermal runaway conditions. The regulator is protected against voltage transients ranging from -50V to +40V. Short circuit current is limited to 1.2A (typ). The CS8122 is an improved replacement for the CS8126 and features a tighter tolerance on its output voltage (2% vs 4%). The CS8122 is packaged in a 5 lead TO220 with copper tab. The copper tab can be connected to a heat sink if necessary.
Features
s 5V +/- 2% Regulated Output s Low Dropout Voltage (0.6V @ 0.5A) s 750mA Output Current Capability s Externally Programmed RESET Delay s Fault Protection Reverse Battery 60V Load Dump -50V Reverse Transient Short Circuit Thermal Shutdown
Block Diagram
VIN
Over Voltage Shutdown
Package Options
5 Lead TO-220
VOUT
PreRegulator Regulated Supply for Circuit Bias + + Charge Current Generator Thermal Shutdown Latching Discharge Bandgap Reference Error Amplifier Anti-Saturation and Current Limit
VOUTSENSE
Delay
Q VDISC S R + Delay Comparator +
1 2 3 4 5
1
RESET
VIN VOUT Gnd Delay RESET
Gnd
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. 2/5/99
1
A
Company
CS8122
Absolute Maximum Ratings Input Operating Range..................................................................................................................................................-0.5 to 26V Power Dissipation.............................................................................................................................................Internally Limited Transient Input Voltage .................................................................................................................................................-50V, 60V Output Current .................................................................................................................................................Internally Limited ESD Susceptibility (Human Body Model)..............................................................................................................................4kV Junction Temperature .............................................................................................................................................-55C to 150C Storage Temperature...............................................................................................................................................-55C to 150C Lead Temperature Soldering Wave Solder (through hole styles only) .....................................................................................10 sec. max, 260C peak Electrical Characteristics: -40uC TA +125uC, -40uC TJ +150uC, 6V VIN 26V, 5mA IOUT 500mA, R RESET = 4.7k1/2 to VCC unless otherwise noted*
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
s
Output Stage (VOUT) Output Voltage Dropout Voltage Supply Current IOUT = 500mA IOUT 10mA IOUT 100mA IOUT 500mA 6V VIN 26V, IOUT = 50mA 50mA IOUT 500mA, VIN = 14V f = 120Hz, VIN = 7 to 17V, IOUT = 250mA 54 0.75 32 VOUT 5.5V VOUT -0.6V, 101/2 Load 1% Duty Cycle, T < 100ms, 101/2 Load Guaranteed by Design 60 -15 -50 150 95 -30 -80 180 210 4.9 5.0 0.35 2 6 55 5 10 75 1.20 40 5.1 0.60 7 12 100 50 50 V V mA
Line Regulation Load Regulation Ripple Rejection Current Limit Overvoltage Shutdown Maximum Line Transient Reverse Polarity Input Voltage DC Reverse Polarity Input Voltage Transient Thermal Shutdown s RESET and Delay Functions Delay Charge Current RESET Threshold RESET Hysteresis Delay Threshold Delay Hysteresis RESET Output Voltage Low RESET Output Leakage Delay Capacitor Discharge Voltage Delay Time
mV mV dB A V V V V C
VDELAY = 2V VOUT Increasing, VRT(ON) VOUT Decreasing, VRT(OFF) VRH = VRT(ON) - VRT(OFF) Charge, VDC(HI) Discharge, VDC(L) 1V < VOUT < VRT(L), 3k1/2 to VOUT VOUT > VRT(H) Current Discharge Latched OONO, VOUT > VRT CDELAY = 0.1F
5 4.65 4.50 150 3.25 2.85 200 0
10 4.90 4.70 200 3.50 3.10 400 0.1
15 VOUT-0.01 VOUT-0.16 250 3.75 3.35 800 0.4 10
A V V mV V V mV V A V ms
0.2 16 32
0.5 48
* To observe safe operating junction temperatures, low duty cycle pulse testing is used in tests where applicable. CDelay x VDelay Threshold Charge = CDelay x 3.5 x 105 (typ) Delay Time = ICharge 2
CS8122
Package Lead Description
PACKAGE LEAD # LEAD SYMBOL FUNCTION
5Lead TO-220 1 2 3 4 5 VIN VOUT Gnd Delay RESET Unregulated supply voltage to IC. Regulated 5V output. Ground connection. Timing capacitor for RESET function. CMOS/TTL compatible output lead. RESET goes low whenever VOUT drops below 6% of it's regulated value.
Typical Performance Characteristics
Quiescent Current vs Input Voltage over Temperature
55.0 50.0 45.0
Quiescent Current (mA)
Quiescent Current vs Input Voltage over Load Resistance
120.0 100.0
Quiescent Current (mA)
Rload = 25W
Room Temp. Rload = 6.67W
40.0 35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
VIN (V) 25uC -40uC 125uC
80.0 60.0 40.0 20.0 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
VIN (V) Rload = 25W Rload = NO LOAD
Rload = 10W
Output Voltage vs Input Voltage over Temperature
Rload = 25W
VOUT vs. VIN over RLOAD
5.5 5.0 4.5 4.0 3.5
VOUT (V) Rload = 6.67W
5.5 5.0 4.5 4.0 3.5
VOUT (V)
Room Temp.
Rload=251/2
3.0 2.5 2.0 1.5 1.0 0.5 0.0
3.0 2.5 2.0 1.5
Rload = NO LOAD Rload = 10W
125uC
25uC -40uC
1.0 0.5 0.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
VIN (V)
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
VIN (V)
3
CS8122
Typical Performance Characteristics: continued
Line Regulation vs. Output Current Load Regulation vs. Output Current
100 80 40 20 0 -20 -40 -60 -80 -100 0 100 200 300 400 500 600 700 800
OUTPUT CURRENT (mA) TEMP = 125uC VIN 6-26V TEMP = 25uC TEMP = - 40uC LOAD REGULATION (mV) LINE REGULATION (mV)
6 4 2 0 -2 -4 -6 -8 -10 -12 -14 0 100 200 300 400 500 600 700 800
OUTPUT CURRENT (mA) VIN = 14V TEMP = 125uC TEMP = 25uC TEMP = -40uC
60
Dropout Voltage vs. Output Current
Quiescent Current vs. Output Current
900
QUIESCENT CURRENT (mA)
100 90 80 70 60 50 40 30 20 10 0 0 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800
OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) -40uC VIN = 14V 25uC 125uC
800
DROPOUT VOLTAGE (mV)
700 600 500 400 300 200 100 0
-40uC 125uC 25uC
Ripple Rejection
IOUT= 250mA
Output Capacitor ESR
103 102
90 80 70
REJECTION (dB) COUT= 10mF, ESR = 1 & 0.1mF, ESR = 0
101
ESR (ohms)
CO= 47/68mF Stable Region
60 50 40 30 20 10 0 100 101 102 103 104 105 106 107 108
FREQUENCY (Hz) COUT= 10mF, ESR = 10W COUT= 10mF, ESR = 1W
100 10-1 10 10
-2
CO= 47mF CO= 68mF
-3
10-4 100
101
102
103
Output Current (mA)
4
CS8122
RESET Circuit Waveform
VOUT VRT(ON) VRT(OFF) VRH
RESET
(1) (2) VRL
(1) = No Delay Capacitor (2) = With Delay Capacitor (3) = Max: RESET Voltage (1.0V)
(3)
tDelay Delay VDH VDC(HI) VDC(LO) (2) VDIS
Circuit Description The CS8122 RESET function, has hysteresis on both the reset and delay comparators, a latching Delay capacitor discharge circuit, and operates down to 1V. The RESET circuit output is an open collector type with ON and OFF parameters as specified. The RESET output NPN transistor is controlled by the two circuits described (see Block Diagram).
Low Voltage Inhibit Circuit Reset Delay Circuit
The Low Voltage Inhibit Circuit monitors output voltage, and when output voltage is below the specified minimum, causes the RESET output transistor to be in the ON (saturation) state. When the output voltage is above the specified level, this circuit permits the RESET output transistor to go into the OFF state if allowed by the RESET Delay circuit.
The Reset Delay Circuit provides a programmable (by external capacitor) delay on the RESET output lead. The Delay lead provides source current to the external delay capacitor only when the Low Voltage Inhibit circuit indicates that output voltage is above VRT(ON). Otherwise, the Delay lead sinks current to ground (used to discharge the delay capacitor). The discharge current is latched ON when the output voltage is below VRT(OFF). The Delay capacitor is fully discharged anytime the output voltage falls out of regulation, even for a short period of time. This feature ensures that a controlled RESET pulse is generated following detection of an error condition. The circuit allows the RESET output transistor to go to the OFF (open) state only when the voltage on the Delay lead is higher than VDC(HI).
Test Circuit
VIN
CIN* 100nF
VOUT
CS8122
Delay RESET
RRST 4.7kW
COUT** 10mF
Gnd
CDelay 0.1mF
*CIN required if regulator is far from power source filter. **COUT required for stability. 5
CS8122
Application Notes 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 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 instability. 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 the test and applications circuit should work for most applications, however it is not necessarily the optimized 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 6 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. Calculating Power Dissipation in a Single Output Linear Regulator The maximum power dissipation for a single output regulator (Figure 1) is: (1) 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, 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
Smart Regulator
IOUT VOUT
}
Control Features
IQ
Figure 1: Single output regulator with key performance parameters labeled.
CS8122
Application Notes: continued Heat Sinks 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 will have a thermal resistance. Like series electrical resistances, these resistances are summed to determine the value of RQJA: RQJA = RQJC + RQCS + RQSA (3) 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 heat sink data sheets of heat sink manufacturers.
7
CS8122
Package Specification
PACKAGE DIMENSIONS IN mm(INCHES) PACKAGE THERMAL DATA
5 Lead TO-220 (T) Straight
Thermal Data RQJC typ RQJA typ
5 Lead TO-220 2.1 50
uC/W uC/W
10.54 (.415) 9.78 (.385) 2.87 (.113) 6.55 (.258) 2.62 (.103) 5.94 (.234)
4.83 (.190) 4.06 (.160) 3.96 (.156) 3.71 (.146)
1.40 (.055) 1.14 (.045)
5 Lead TO-220 (TVA) Vertical
4.83 (.190) 4.06 (.160) 10.54 (.415) 9.78 (.385) 3.96 (.156) 3.71 (.146)
1.40 (.055) 1.14 (.045)
14.99 (.590) 14.22 (.560)
6.55 (.258) 5.94 (.234) 2.87 (.113) 2.62 (.103) 14.99 (.590) 14.22 (.560)
14.22 (.560) 13.72 (.540)
1.78 (.070) 2.92 (.115) 2.29 (.090)
1.02 (.040) 0.76 (.030)
8.64 (.340) 7.87 (.310)
4.34 (.171) 1.68 (.066) typ 6.80 (.268) 0.56 (.022) 0.36 (.014) 7.51 (.296)
1.02(.040) 0.63(.025) 6.93(.273) 6.68(.263)
1.83(.072) 1.57(.062)
0.56 (.022) 0.36 (.014) 2.92 (.115) 2.29 (.090)
1.70 (.067)
.94 (.037) .69 (.027)
5 Lead TO-220 (THA) Horizontal
4.83 (.190) 10.54 (.415) 9.78 (.385) 2.87 (.113) 2.62 (.103) 1.40 (.055) 3.96 (.156) 3.71 (.146) 1.14 (.045) 4.06 (.160)
6.55 (.258) 5.94 (.234)
14.99 (.590) 14.22 (.560)
2.77 (.109) 6.83 (.269)
0.81(.032)
1.68 (.066) TYP 1.70 (.067) 6.81(.268)
0.56 (.022) 0.36 (.014) 6.60 (.260) 5.84 (.230)
2.92 (.115) 2.29 (.090)
Ordering Information
Part Number CS8122YT5 CS8122YTHA5 CS8122YTVA5
Rev. 2/5/99
Description 5 Lead TO-220 Straight 5 Lead TO-220 Horizontal 5 Lead TO-220 Vertical 8
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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