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CS403
CS403
5V, 750mA Linear Regulator with RESET
Description
The CS403 is a linear regulator specially designed as a post regulator. The CS403 provides low noise, low drift, and high accuracy to improve the performance of a switching power supply. It is ideal for applications requiring a highly efficient and accurate linear regulator. The active RESET makes the device particularly well suited to supply microprocessor based systems. The PNP-NPN output stage assures a low dropout voltage without requiring excessive supply current. Its features include low dropout (1V typically) and low supply drain (4mA typical with IOUT = 500mA). The CS403 design optimizes supply rejection by switching the internal reference from the supply input to the regulator output as soon as the nominal output voltage is reached.
Features
s 5V 5% Output Voltage s Low Drift s High Efficiency s Short Circuit Protection s Active Delayed Reset s Noise Immunity on Reset s 750mA Output Current
Absolute Maximum Ratings Forward Input Voltage ..................................................................................18V Operating Junction Temperature, TJ ..............................................-40 to 150uC Storage Temperature........................................................................-55 to 150uC Lead Temperature Soldering Wave Solder (through hole styles only)..........10 sec. max, 260C peak Block Diagram
Package Options
5 Lead TO-220
Tab (Gnd)
V OUT Output Current Limit
V IN
Start
1. VIN
+ REF TO VOUT + Error Amp ICHARGE SCR Latch Delay
2. RESET 3. Gnd 4. Delay 5. VOUT
Low Voltage INHIBIT Comparator
RESET Delay Comparator + VCMP Gnd
1
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. 2/18/98
1
A
Company
CS403
Electrical Characteristics : Refer to the test circuit, -40C TC 125C, -40 TJ 150C, 7V VIN 10V unless otherwise specified
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Output Voltage, VOUT
VIN = 8.5V, IOUT = 250mA TJ = 25C 100mA IOUT 750mA 100 to 750mA 100mA IOUT 750mA, VIN = 8.5V IOUT = 750mA IOUT = 0mA IOUT = 750mA IOUT-250mA f = 120Hz COUT = 10F, VIN = 8.5VVpp IR = 1.6mA 1.0 VOUT 4.75V Cd = 100nF VOUT Increasing VOUT Decreasing Charge Discharge
4.95 4.85 -0.75
5.00 5.00 30 1.4 3 5 70 1 0.08 0
5.05 5.15 18.0 100 1.8 4 25
V V mV V mA mA dB A
Operating Input Voltage Load Regulation Dropout Voltage Quiescent Current PSRR Output Short Circuit Current Reset Output Voltage Delay Time for Reset Output Reset Threshold: VRTH VRTL Threshold Hysteresis Delay, VDTC Delay, VDTD Delay Hysteresis, VDH Reset Delay Capacitor Charging Current, ICH Reset Delay Capacitor Discharge Voltage, VDIS td = Cd x VDTC/Ich = CDelay x 2.105 (typical) where: td Cd VDTC Ich = = = =
0.40 50 30 VOUT-0.04
V A ms V V mV V V mV A V
Reset Output Leakage Current VOUT in regulation 10 4.75 10 3.7 3.1 200 10
20
50 4.0 3.5 500 20 0.6 4.4 3.9 1000 40 1.2
Time delay Value of external charging capacitor (see test circuit). Delay threshold charge Reset delay capacitor charging current.
Package Lead Description
PACKAGE LEAD # LEAD SYMBOL FUNCTION
5 Lead TO-220 1 2 3 4 5 VIN RESET Gnd Delay VOUT Input voltage. CMOS compatible output lead. RESET goes low whenever VOUT falls out of regulation. Ground connection. Timing capacitor for RESET function. Regulated output voltage, 5V (typ).
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CS403
Typical Performance Characteristics
5.5 4.5
22.0
1.2 TA = -40uC 1.0
Dropout Voltage (V)
VO
Supply Current (mA)
18.0
3.5
14.0 IQ
0.8 0.6 0.4 0.2
TA = 25uC
VOUT
2.5 1.5
10.0
6.0
0.0 0.0 2.0 4.0 6.0 8.0
0.0 10.0
0.0 0 100 200 300 400 500
VIN
Output Current (mA), IOUT
Output Voltage vs. VIN , IQ
Dropout Voltage vs. Output Current Over Temperature
5.02 IOUT = 250mA 5.01 5.00
VOUT (V)
4.99 4.98 4.97 4.96 4.95 -40
0
40
80
120
150
Junction Temperature (uC), TJ
Output Voltage vs. Junction Temperature
Reset Circuit Waveform
VOUT
VRT(ON) VRT(OFF)
VRH
RESET
(3) VRL
(1) (2)
TDelay
Delay
VDTC VDTD VDH VDIS (2)
(1) - No Delay Capacitor. (2) - With Delay Capacitor. (3) - Max. Reset Voltage (<1.0V)
3
CS403
Circuit Description The CS403 RESET function is very precise, 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 This 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. Reset Delay Circuit This circuit provides a programmable (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), or when the voltage on the Delay capacitor is above VDIS. In other words, the Delay capacitor is fully discharged any time the output voltage falls out of regulation, even for a short period of time. This feature ensures 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 VDIS.
Test Circuit
VIN C 1* 100nF
VOUT C2** COUT =10mF to 100mF
CS403
Delay Gnd RESET
100nF
Cd
C1* is required if the regulator is far from the power source filter. C2** is required for stability
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. 4 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
CS403
Application Notes 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. Calculating Power Dissipation in a Single Output Linear Regulator sible 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.
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 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.
The maximum power dissipation for a single output regulator (Figure 1) is:
PD(max) = VIN(max) - VOUT(min) IOUT(max) + VIN(max)IQ
{
}
(1)
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 permis-
5
CS403
Package Specification
PACKAGE DIMENSIONS IN mm(INCHES) PACKAGE THERMAL DATA
Thermal Data RQJC typ RQJA typ
TO-220 4.1 50
uC/W uC/W
5 Lead TO-220 (T) Straight
5 Lead TO-220 (THA) Horizontal
4.83 (.190) 10.54 (.415) 9.78 (.385) 1.40 (.055) 3.96 (.156) 3.71 (.146) 1.14 (.045) 4.06 (.160)
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)
2.87 (.113) 2.62 (.103)
6.55 (.258) 5.94 (.234)
14.99 (.590) 14.22 (.560)
14.99 (.590) 14.22 (.560)
2.77 (.109) 6.83 (.269)
14.22 (.560) 13.72 (.540)
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)
1.02 (.040) 0.76 (.030)
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)
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)
6.55 (.258) 5.94 (.234) 2.87 (.113) 2.62 (.103) 14.99 (.590) 14.22 (.560)
1.78 (.070) 2.92 (.115) 2.29 (.090) 8.64 (.340) 7.87 (.310) 0.56 (.022) 0.36 (.014)
4.34 (.171) 7.51 (.296) 1.68 (.066) typ 6.80 (.268)
1.70 (.067)
.94 (.037) .69 (.027)
Ordering Information
Part Number CS403GT5 CS403GTVA5 CS403GTHA5
Rev. 2/18/98
Description TO-220 Straight TO-220 Vertical TO-220 Horizontal 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

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