1.0A Step-Down Switching Regulator
TC2575
TC2575
1.0A Step-Down Switching Regulator
FEATURES
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3.3V, 5.0V, 12V, and Adjustable Output Versions
Adjustable Version Output Voltage Range of
1.23V to 37V
±
4% Max. Over Line and Load Conditions
Guaranteed 1.0 A Output Current
Wide Input Voltage Range; 4.75V to 40V
Requires Only 4 External Components
52kHz Fixed Frequency Internal Oscillator
TTL Shutdown Capability, Low Power Standby Mode
High Efficiency
Uses Readily Available Standard Inductors
Thermal Shutdown and Current Limit Protection
The TC2575 series of regulators are monolithic inte-
grated circuits ideally suited for easy and convenient design
of a step–down switching regulator (buck converter). All
circuits of this series are capable of driving a 1.0A load with
excellent line and load regulation. These devices are avail-
able in fixed output voltages of 3.3V, 5.0V, 12V, and
an adjustable output version.
These regulators were designed to minimize the num-
ber of external components to simplify the power supply
design. Standard series of inductors optimized for use with
the TC2575 are offered by several different inductor manu-
facturers.
Since the TC2575 converter is a switch-mode power
supply, its efficiency is significantly higher in comparison
with popular three-terminal linear regulators, especially with
higher input voltages. In many cases, the power dissipated
is so low, that no heatsinking is required or its size can be
reduced dramatically.
The TC2575 features include a guaranteed
±4%
toler-
ance on output voltage within specified input voltages and
output load conditions, and
±10%
on the oscillator frequency
(±2% over 0°C to +125°C). External shutdown is included,
featuring 80µA (typical) standby current. The output switch
includes cycle-by-cycle current limiting, as well as thermal
shutdown for full protection under fault conditions.
APPLICATIONS
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Simple and High-Efficiency Step-Down
(Buck) Regulator
Efficient Pre–Regulator for Linear Regulators
On–Card Switching Regulators
Positive to Negative Converters (Buck–Boost)
Negative Step-Up Converters
Power Supply for Battery Chargers
GENERAL DESCRIPTION
PIN CONFIGURATIONS
5-Pin TO-220
ORDERING INFORMATION
Part
Number
TC2575-3.3VAT
TC2575-5.0VAT
TC2575-12.0VAT*
TC2575VAT**
Package
5-Pin TO-220
5-Pin TO-220
5-Pin TO-220
5-Pin TO-220
Temperature
Range
–40 to +125°C
–40 to +125°C
–40 to +125°C
–40 to +125°C
TC2575
Note: * Contact factory for availability
** ADJ = 1.23 To 37V.
1 2 3 4 5
TC2575-1 3/13/00
TelCom Semiconductor reserves the right to make changes in the circuitry and specifications of its devices.
1
OUTPUT
GND
FEEDBACK
ON/OFF
V
IN
1.0A Step-Down Switching Regulator
TC2575
ABSOLUTE MAXIMUM RATINGS*
Maximum Supply Voltage ................................ V
IN
= 45V
ON/OFF Pin Input Voltage ..................... –0.3V
≤
V
≤
+V
IN
Output Voltage to Ground (Steady State) ............... –1.0 V
Max Power Dissipation(TO-220) ......... (Internally Limited)
Thermal Resistance, Junction-to-Ambient ..... 65°C/W
Thermal Resistance, Junction-to-Case ........ 5.0°C/W
Storage Temperature Range ................. –65°C to +150°C
Minimum ESD Rating ............................................. 3.0 kV
(Human Body Model: C = 100pF, R = 1.5kΩ)
Lead Temperature (Soldering, 10 seconds) .......... 260
°C
Maximum Junction Temperature............................. 150°C
Operating Junction Temperature Range .... –40 to +125*C
Supply Voltage ............................................................40V
*This is a stress rating only, and functional operation of the device at these
or any other conditions beyond those indicated in the operation section of
the specifications is not implied. Exposure to absolute maximum ratings
conditions for extended periods of time may affect device reliability.
ELECTRICAL CHARACTERISTICS:
(Unless otherwise specified, V
IN
= 12V for the 3.3V, 5.0V, and Adjustable
version,V
IN
= 25V for the 12V version. I
LOAD
= 200mA. For typical values T
J
= 25°C, for min/max values T
J
is the operating
junction temperature range that applies (Note 2), unless otherwise noted.
Symbol
V
OUT
Parameter
Output Voltage
Test Conditions
V
IN
= 12V, I
LOAD
= 0.2A, T
J
= 25°C
4.75V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
1.0A
T
J
= 25°C
T
J
= –40°C to +125°
V
IN
= 12V, I
LOAD
= 1.0A
V
IN
= 12V, I
LOAD
= 0.2A, T
J
= 25°C
8.0V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
1.0A
T
J
= 25°C
T
J
= –40°C to +125°C
V
IN
= 12V, I
LOAD
= 1.0 A
V
IN
= 25V, I
LOAD
= 0.2A, T
J
= 25°C
15V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
1.0A
T
J
= 25°C
T
J
= –40°C to +125°C
V
IN
= 15V, I
LOAD
= 1.0 A
V
IN
= 12V, I
LOAD
= 0.2A, V
OUT
= 5.0V,
T
J
= 25°C
8.0V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
1.0A
V
OUT
= 5.0V
T
J
= 25°C
T
J
= –40°C to +125°C
V
IN
= 12V, I
LOAD
= 1.0A, V
OUT
= 5.0V
Min
3.234
3.168
3.135
—
4.9
4.8
4.75
—
11.76
11.52
11.4
—
1.217
Typ
3.3
3.3
—
75
5.0
5.0
—
77
12
12
—
88
1.23
Max
3.366
3.432
3.465
—
5.1
5.2
5.25
—
12.24
12.48
12.6
—
1.243
Units
V
TC2575-3.3 [(Note 1) Test Circuit Figure 2]
η
V
OUT
Efficiency
Output Voltage
%
V
TC2575-5 [(Note 1)Test Circuit Figure 2]
η
V
OUT
Efficiency
Output Voltage
%
V
TC2575-12 [(Note 1) Test Circuit Figure 2]
η
V
FB
V
FB
Efficiency
Feedback Voltage
Feedback Voltage
%
V
TC2575-Adjustable Version [(Note 1) Test Circuit Figure 2]
η
Efficiency
1.193
1.18
—
1.23
—
77
1.267
1.28
—
%
NOTES:
1. External components such as the catch diode, inductor, input and output capacitors can affect the switching regulator system
performance. When the TC2575 is used as shown in the Figure 2 test circuit, the system performance will be as
shown in the system parameters section of the Electrical Characteristics.
2. Tested junction temperature range for the TC2575: T
LOW
= –40°C T
HIGH
= +125°C
TC2575-1 3/13/00
2
1.0A Step-Down Switching Regulator
TC2575
ELECTRICAL CHARACTERISTICS:
(Unless otherwise specified, V
IN
= 12V for the 3.3V, 5.0V, and Adjustable
version,V
IN
= 25V for the 12V version. I
LOAD
= 200mA. For typical values T
J
= 25°C, for min/max values T
J
is the operat-
ing junction temperature range that applies (Note 2), unless otherwise noted.
Symbol
I
b
Parameter
Feedback Bias Current
Test Conditions
Min
Typ
Max
Units
nA
TC2575-ALL OUTPUT VOLTAGE VERSIONS
V
OUT
= 5.0V (Adjustable Version Only)
T
J
= 25°C
T
J
= –40°C to +125°C
Oscillator Frequency (Note 3)
T
J
= 25°C
T
J
= 0 to +125°C
T
J
= –40 to +125°C
Saturation Voltage
I
OUT
= 1.0A, (Note 4)
T
J
= 25°C
T
J
= –40 to +125°C
Max Duty Cycle (“on”) [Note 5]
Current Limit Peak Current
(Notes 3 and 4)
T
J
= 25°C
T
J
= –40 to +125°C
Output Leakage Current
(Notes 6 and 7), T
J
= 25°C
Output = 0 V
Output = – 1.0 V
Quiescent Current (Note 6)
T
J
= 25°C
T
J
= –40 to +125°C
Standby Quiescent Current,
ON/OFF Pin = 5.0 V (“off”)
T
J
= 25°C
T
J
= –40 to +125°C
ON/OFF Pin Logic Input Level
(Test Figure 2)
V
OUT
= 0V
T
J
= 25°C
T
J
= –40 to +125°C
Nominal Output Voltage
V
OUT
= Nominal Output Voltage
T
J
= 25°C
T
J
= –40 to +125°C
ON/OFF Pin Input Current
(Test Figure 2)
ON/OFF Pin = 5.0V (“off”),
T
J
= 25°C
ON/OFF Pin Input Current
ON/OFF Pin = 0V (“on”),
T
J
= 25°C
—
—
—
47
42
—
—
94
1.7
1.4
—
—
—
—
—
—
25
—
52
—
—
1.0
—
98
2.3
—
0.8
6.0
5.0
—
80
—
100
200
—
58
63
1.2
1.3
—
3.0
3.2
mA
2.0
20
mA
9.0
11
µA
200
400
V
2.2
2.4
—
—
—
—
1.4
—
1.2
—
15
0
—
—
V
1.0
0.8
µA
30
5.0
µA
f
OSC
kHz
V
SAT
V
DC
I
CL
%
A
I
L
I
Q
I
STBY
V
IH
V
IL
I
IH
I
IL
NOTES:
3. The oscillator frequency reduces to approximately 18kHz in the event of an output short or an overload which causes the regulated
output voltage to drop approximately 40% from the nominal output voltage. This self protection feature lowers the average power
dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%.
4. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to the output pin.
5. Feedback (Pin 4) removed from output and connected to 0V.
6. Feedback (Pin 4) removed from output and connected to +12V for the Adjustable, 3.3V, and 5.0V versions, and 25V for the 12V,
to force the output transistor "OFF".
7. V
IN
= 40 V.
TC2575-1 3/13/00
3
1.0A Step-Down Switching Regulator
TC2575
PIN DESCRIPTION
Pin No.
5-Pin TO-220
1
Symbol
V
IN
Description
This pin is the positive input supply for the TC2575 step-down
switching regulator. In order to minimize voltage transients and to
supply the switching currents needed by the regulator, a suitable
input bypass capacitor must be present (C
IN
in Figure 1).
This is the emitter of the internal switch. The saturation voltage
V
SAT
of this output switch is typically 1.0V. It should be kept in
mind that the PCB area connected to this pin should be kept to a
minimum in order to minimize coupling to sensitive circuitry.
Circuit ground pin. See the information about the printed circuit
boad layout.
This pin senses regulated output voltage to complete the
feedback loop. The signal is divided by the internal resistor
divider network R2, R1 and applied to the non-inverting input of
the internal error amplifier. In the adjustable version of the
TC2575 switching regulator this pin is the direct input of the error
amplifier and the resistor network R2, R1 is connected externally
to allow programming of the output voltage.
It allows the switching regulator circuit to be shut down using
logic level signals, thus dropping the total input supply current to
approximately 80µA. The threshold voltage is typically 1.4V.
Applying a voltage above this value (up to +V
IN
) shuts the
regulator off. If the voltage applied to this pin is lower than 1.4V
or if this pin is left open, the regulator will be in the "on" condition.
2
Output
3
4
GND
Feedback
5
ON/OFF
REPRESENTATIVE BLOCK DIAGRAM AND TYPICAL APPLICATION
+VIN
Unregulated
DC Input
CIN
+
1
TC2575
4
3.1V Internal
Regulator
ON/OFF
ON/OFF
5
Output
Voltage Versions
Fixed gain
Error Amplifier
Current
Limit
Comparator
R2 (Ω)
Feedback
R2
+
–
Driver
+
R1
1.0k
–
Freq.
Shift
18kHz
1.235V
Band-Gap
Reference
+
–
Latch
3.3V
1.7k
5.0V
3.1k
12V
8.84k
15V
11.3k
For Adjustable version
R1 = open, R2 = 0Ω
Output
1.0 Amp
Switch
2
GND
3
L1
Regulated
Output
VOUT
D1
+
COUT
Load
52kHz
Oscillator
Reset
Thermal
Shutdown
TC2575-1 3/13/00
4
1.0A Step-Down Switching Regulator
TC2575
Feedback
7.0 – 40V
Unregulated
DC Input
+VIN
CIN
100µF
4
TC2575
3 GND
Output
2
5 ON/OFF
L1
330µH
5.0V Regulated
Output 1.0A Load
D1
1N5819
COUT
330µF
+
1
Figure 1. Block Diagram and Typical Application: Fixed Output Voltages
5.0 Output Voltage Versions
Feedback
VIN
1
VIN
Unregulated
DC Input
8.0 – 40V
+
TC2575
(5V)
5
4
Output
2
ON/OFF
L1
330µH
COUT +
D1
330µF/16V
IN5819
VOUT
Regulated
Output
3 GND
CIN
100µF/50V
Load
Adjustable Output Voltage Versions
Feedback
VIN
1
Unregulated
DC Input
8.0 – 40V
+
3
4
TC2575
Adjustable
GND
5
Output
2
ON/OFF
D1
IN5819
L1
330µH
VOUT
Regulated
Output
+ CIN
330µF/
16V
R2
Load
R1
CIN
100µF/50V
VOUT = VREF
R2
(
1 + R1
)
R1= R2
(
VOUT - 1
)
VREF
Where VREF = 1.23V, R1
between 1.0kΩ and 5.0kΩ
Figure 2. Typical Test Circuit
TC2575-1 3/13/00
5
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