CHERRY CS403GT5

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
Features
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.
■ 5V ±5% Output Voltage
■ Low Drift
■ High Efficiency
■ Short Circuit Protection
■ Active Delayed Reset
■ Noise Immunity on Reset
■ 750mA Output Current
Absolute Maximum Ratings
Forward Input Voltage ..................................................................................18V
Operating Junction Temperature, TJ ..............................................-40 to 150ûC
Storage Temperature........................................................................-55 to 150ûC
Lead Temperature Soldering
Wave Solder (through hole styles only)..........10 sec. max, 260¡C peak
Package Options
Block Diagram
5 Lead TO-220
Tab (Gnd)
V OUT
V IN
Output
Current
Limit
Start
1. VIN
+
REF
-
+
TO VOUT
-
Error Amp
2. RESET
ICHARGE
3. Gnd
SCR
Latch
Low Voltage
INHIBIT
Comparator
Delay
4. Delay
5. VOUT
RESET
Delay
Comparator
1
+
VCMP
Gnd
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: [email protected]
Web Site: www.cherry-semi.com
Rev. 2/18/98
1
A
¨
Company
CS403
Electrical Characteristics : Refer to the test circuit, -40¡C ² TC ² 125¡C, -40 ² TJ ² 150¡C, 7V ² VIN ² 10V unless otherwise specified
PARAMETER
MIN
TYP
MAX
UNIT
VIN = 8.5V, IOUT = 250mA
TJ = 25¡C
100mA ² IOUT ² 750mA
4.95
4.85
5.00
5.00
5.05
5.15
V
Operating Input Voltage
100 to 750mA
-0.75
18.0
V
Load Regulation
100mA ² IOUT ² 750mA, VIN = 8.5V
30
100
mV
Output Voltage, VOUT
TEST CONDITIONS
Dropout Voltage
IOUT = 750mA
1.4
1.8
V
Quiescent Current
IOUT = 0mA
IOUT = 750mA
3
5
4
25
mA
mA
PSRR
IOUT-250mA f = 120Hz
COUT = 10µF, VIN = 8.5V±Vpp
70
IR = 1.6mA 1.0 ² VOUT ² 4.75V
0.08
0.40
V
0
50
µA
30
ms
VOUT-0.04
V
V
Output Short Circuit Current
Reset Output Voltage
dB
1
Reset Output Leakage Current VOUT in regulation
Delay Time for Reset Output
Cd = 100nF
Reset Threshold: VRTH
VRTL
VOUT Increasing
VOUT Decreasing
10
20
A
4.75
Threshold Hysteresis
10
50
3.7
3.1
4.0
3.5
4.4
3.9
V
V
Delay Hysteresis, VDH
200
500
1000
mV
Reset Delay Capacitor
Charging Current, ICH
10
20
40
µA
0.6
1.2
V
Delay, VDTC
Delay, VDTD
Charge
Discharge
Reset Delay Capacitor
Discharge Voltage, VDIS
mV
td = Cd x VDTC/Ich
= CDelay x 2.105 (typical)
where:
td
Cd
VDTC
Ich
=
=
=
=
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
VIN
Input voltage.
2
RESET
CMOS compatible output lead. RESET goes low whenever VOUT
falls out of regulation.
3
Gnd
Ground connection.
4
Delay
Timing capacitor for RESET function.
5
VOUT
Regulated output voltage, 5V (typ).
2
CS403
Typical Performance Characteristics
5.5
22.0
1.2
4.5
18.0
1.0
VOUT
3.5
14.0
IQ
2.5
10.0
1.5
6.0
Dropout Voltage (V)
VO
Supply Current (mA)
TA = -40ûC
TA = 25ûC
0.8
0.6
0.4
0.2
0.0
0.0
2.0
4.0
6.0
8.0
0.0
10.0
0.0
0
VIN
100
200
300
Dropout Voltage vs. Output Current Over Temperature
Output Voltage vs. VIN , IQ
5.02
IOUT = 250mA
5.01
VOUT (V)
5.00
4.99
4.98
4.97
4.96
4.95
-40
400
Output Current (mA), IOUT
0
40
80
120
150
Junction Temperature (ûC), TJ
Output Voltage vs. Junction Temperature
Reset Circuit Waveform
VOUT
VRT(ON)
VRT(OFF)
VRH
(1)
RESET
(2)
(3)
VRL
TDelay
Delay
VDTC
VDTD
VDH
VDIS
(2)
(1) - No Delay Capacitor.
(2) - With Delay Capacitor.
(3) - Max. Reset Voltage (<1.0V)
3
500
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.
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.
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.
Test Circuit
VOUT
VIN
C 1*
100nF
CS403
C2**
COUT =10mF to
100mF
RESET
Delay
Gnd
100nF
Cd
C1* is required if the regulator is far from the power source filter.
C2** is required for stability
Application Notes
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
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 (-25¡C to -40¡C), both the value and ESR of the
capacitor will vary considerably. The capacitor manufacturers data sheet usually provides this information.
4
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.
sible value of RQJA can be calculated:
RQJA =
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 junctionÐtoÐcase thermal resistance,
RQCS = the caseÐtoÐheatsink thermal resistance, and
RQSA = the heatsinkÐtoÐambient 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:
{
(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 150¡C.
Calculating Power Dissipation
in a Single Output Linear Regulator
PD(max) = VIN(max) - VOUT(min) IOUT(max) + VIN(max)IQ
150¡C - TA
PD
(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
ûC/W
ûC/W
5 Lead TO-220 (THA) Horizontal
5 Lead TO-220 (T) Straight
4.83 (.190)
10.54 (.415)
9.78 (.385)
10.54 (.415)
9.78 (.385)
2.87 (.113)
6.55 (.258) 2.62 (.103)
5.94 (.234)
4.83 (.190)
4.06 (.160)
2.87 (.113)
2.62 (.103)
1.40 (.055)
1.14 (.045)
3.96 (.156)
3.71 (.146)
1.40 (.055)
4.06 (.160)
1.14 (.045)
3.96 (.156)
3.71 (.146)
14.99 (.590)
14.22 (.560)
6.55 (.258)
5.94 (.234)
14.99 (.590)
14.22 (.560)
2.77 (.109)
6.83 (.269)
14.22 (.560)
13.72 (.540)
1.68
(.066)
TYP
1.70 (.067)
0.81(.032)
2.92 (.115)
2.29 (.090)
0.56 (.022)
0.36 (.014)
6.60 (.260)
5.84 (.230)
6.81(.268)
1.02 (.040)
0.76 (.030)
1.83(.072)
1.57(.062)
1.02(.040)
0.63(.025)
0.56 (.022)
0.36 (.014)
6.93(.273)
6.68(.263)
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)
4.34 (.171)
1.68
(.066) typ
1.70 (.067)
0.56 (.022)
0.36 (.014)
7.51 (.296)
6.80 (.268)
.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
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
© 1999 Cherry Semiconductor Corporation