1
TC2575
TC2575-1 3/13/00
1.0A Step-Down Switching Regulator
1.0A Step-Down Switching Regulator
The TC2575 series of regulators are monolithic inte-
grated circuits ideally suited for easy and convenient design
of a stepdown 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 80
A (typical) standby current. The output switch
includes cycle-by-cycle current limiting, as well as thermal
shutdown for full protection under fault conditions.
FEATURES
s
3.3V, 5.0V, 12V, and Adjustable Output Versions
s
Adjustable Version Output Voltage Range of
1.23V to 37V
4% Max. Over Line and Load Conditions
s
Guaranteed 1.0 A Output Current
s
Wide Input Voltage Range; 4.75V to 40V
s
Requires Only 4 External Components
s
52kHz Fixed Frequency Internal Oscillator
s
TTL Shutdown Capability, Low Power Standby Mode
s
High Efficiency
s
Uses Readily Available Standard Inductors
s
Thermal Shutdown and Current Limit Protection
APPLICATIONS
s
Simple and High-Efficiency Step-Down
(Buck) Regulator
s
Efficient PreRegulator for Linear Regulators
s
OnCard Switching Regulators
s
Positive to Negative Converters (BuckBoost)
s
Negative Step-Up Converters
s
Power Supply for Battery Chargers
GENERAL DESCRIPTION
ORDERING INFORMATION
Part
Temperature
Number
Package Range
TC2575-3.3VAT
5-Pin TO-220
40 to +125
C
TC2575-5.0VAT
5-Pin TO-220
40 to +125
C
TC2575-12.0VAT* 5-Pin TO-220
40 to +125
C
TC2575VAT**
5-Pin TO-220
40 to +125
C
TC2575
TelCom Semiconductor reserves the right to make changes in the circuitry and specifications of its devices.
PIN CONFIGURATIONS
5-Pin TO-220
Note: * Contact factory for availability
** ADJ = 1.23 To 37V.
GND
V
IN
OUTPUT
FEEDBACK
ON/OFF
1 2 3 4 5
TC2575
TC2575
1.0A Step-Down Switching Regulator
2
TC2575-1 3/13/00
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 = 1.5k
)
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
Parameter
Test Conditions
Min
Typ
Max
Units
TC2575-3.3 [(Note 1) Test Circuit Figure 2]
V
OUT
Output Voltage
V
IN
= 12V, I
LOAD
= 0.2A, T
J
= 25
C
3.234
3.3
3.366
V
4.75V
V
IN
40V, 0.2A
I
LOAD
1.0A
T
J
= 25
C
3.168
3.3
3.432
T
J
= 40
C to +125
3.135
--
3.465
Efficiency
V
IN
= 12V, I
LOAD
= 1.0A
--
75
--
%
TC2575-5 [(Note 1)Test Circuit Figure 2]
V
OUT
Output Voltage
V
IN
= 12V, I
LOAD
= 0.2A, T
J
= 25
C
4.9
5.0
5.1
V
8.0V
V
IN
40V, 0.2A
I
LOAD
1.0A
T
J
= 25
C
4.8
5.0
5.2
T
J
= 40
C to +125
C
4.75
--
5.25
Efficiency
V
IN
= 12V, I
LOAD
= 1.0 A
--
77
--
%
TC2575-12 [(Note 1) Test Circuit Figure 2]
V
OUT
Output Voltage
V
IN
= 25V, I
LOAD
= 0.2A, T
J
= 25
C
11.76
12
12.24
V
15V
V
IN
40V, 0.2A
I
LOAD
1.0A
T
J
= 25
C
11.52
12
12.48
T
J
= 40
C to +125
C
11.4
--
12.6
Efficiency
V
IN
= 15V, I
LOAD
= 1.0 A
--
88
--
%
TC2575-Adjustable Version [(Note 1) Test Circuit Figure 2]
V
FB
Feedback Voltage
V
IN
= 12V, I
LOAD
= 0.2A, V
OUT
= 5.0V,
1.217
1.23
1.243
V
T
J
= 25
C
V
FB
Feedback Voltage
8.0V
V
IN
40V, 0.2A
I
LOAD
1.0A
V
OUT
= 5.0V
T
J
= 25
C
1.193
1.23
1.267
T
J
= 40
C to +125
C
1.18
--
1.28
Efficiency
V
IN
= 12V, I
LOAD
= 1.0A, V
OUT
= 5.0V
--
77
--
%
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
3
TC2575
TC2575-1 3/13/00
1.0A Step-Down Switching Regulator
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
Parameter
Test Conditions
Min
Typ
Max
Units
TC2575-ALL OUTPUT VOLTAGE VERSIONS
I
b
Feedback Bias Current
V
OUT
= 5.0V (Adjustable Version Only)
nA
T
J
= 25
C
--
25
100
T
J
= 40
C to +125
C
--
--
200
f
OSC
Oscillator Frequency (Note 3)
T
J
= 25
C
--
52
--
kHz
T
J
= 0 to +125
C
47
--
58
T
J
= 40 to +125
C
42
--
63
V
SAT
Saturation Voltage
I
OUT
= 1.0A, (Note 4)
V
T
J
= 25
C
--
1.0
1.2
T
J
= 40 to +125
C
--
--
1.3
DC
Max Duty Cycle ("on") [Note 5]
94
98
--
%
I
CL
Current Limit Peak Current
A
(Notes 3 and 4)
T
J
= 25
C
1.7
2.3
3.0
T
J
= 40 to +125
C
1.4
--
3.2
I
L
Output Leakage Current
mA
(Notes 6 and 7), T
J
= 25
C
Output = 0 V
--
0.8
2.0
Output = 1.0 V
--
6.0
20
I
Q
Quiescent Current (Note 6)
mA
T
J
= 25
C
--
5.0
9.0
T
J
= 40 to +125
C
--
--
11
I
STBY
Standby Quiescent Current,
A
ON/OFF Pin = 5.0 V ("off")
T
J
= 25
C
--
80
200
T
J
= 40 to +125
C
--
--
400
V
IH
ON/OFF Pin Logic Input Level
V
(Test Figure 2)
V
OUT
= 0V
T
J
= 25
C
2.2
1.4
--
T
J
= 40 to +125
C
2.4
--
--
V
IL
Nominal Output Voltage
V
OUT
= Nominal Output Voltage
V
T
J
= 25
C
--
1.2
1.0
T
J
= 40 to +125
C
--
--
0.8
I
IH
ON/OFF Pin Input Current
A
(Test Figure 2)
ON/OFF Pin = 5.0V ("off"),
--
15
30
T
J
= 25
C
I
IL
ON/OFF Pin Input Current
ON/OFF Pin = 0V ("on"),
--
0
5.0
A
T
J
= 25
C
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
1.0A Step-Down Switching Regulator
4
TC2575-1 3/13/00
REPRESENTATIVE BLOCK DIAGRAM AND TYPICAL APPLICATION
TC2575
+
+
3.1V Internal
Regulator
ON/OFF
ON/OFF
Latch
Freq.
Shift
18kHz
Reset
Thermal
Shutdown
5
2
1.0 Amp
Switch
D1
L1
COUT
+VIN
CIN
VOUT
Driver
Output
GND
4
1
For Adjustable version
R1 = open, R2 = 0
Load
Regulated
Output
Feedback
Unregulated
DC Input
R2
R1
1.0k
Current
Limit
Comparator
Fixed gain
Error Amplifier
+
+
+
52kHz
Oscillator
1.235V
Band-Gap
Reference
3
Output
Voltage Versions
3.3V
5.0V
12V
15V
R2 (
)
1.7k
3.1k
8.84k
11.3k
PIN DESCRIPTION
Pin No.
5-Pin TO-220
Symbol Description
1
V
IN
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).
2
Output
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.
3
GND
Circuit ground pin. See the information about the printed circuit
boad layout.
4
Feedback
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.
5
ON/OFF
It allows the switching regulator circuit to be shut down using
logic level signals, thus dropping the total input supply current to
approximately 80
A. 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.
5
TC2575
TC2575-1 3/13/00
1.0A Step-Down Switching Regulator
CIN
100
F
COUT
330
F
+VIN
1
3 GND
5
2
4
L1
330
H
Output
D1
1N5819
Feedback
ON/OFF
7.0 40V
Unregulated
DC Input
5.0V Regulated
Output 1.0A Load
TC2575
+
Figure 1. Block Diagram and Typical Application: Fixed Output Voltages
Figure 2. Typical Test Circuit
CIN
100
F/50V
COUT
330
F/16V
VOUT
Regulated
Output
VOUT
Regulated
Output
VIN
1
3
GND
5
2
4
D1
IN5819
D1
IN5819
L1
330
H
Output
Feedback
5.0 Output Voltage Versions
VOUT = VREF
(
1 + R2
)
R1
ON/OFF
VIN
Unregulated
DC Input
8.0 40V
TC2575
(5V)
+
+
Load
CIN
100
F/50V
R2
R1
VIN
1
3
GND
5
2
4
L1
330
H
Output
Feedback
Where VREF = 1.23V, R1
between 1.0k
and 5.0k
Adjustable Output Voltage Versions
ON/OFF
Unregulated
DC Input
8.0 40V
TC2575
+
CIN
330
F/
16V
+
Load
Adjustable
R1= R2
(
VOUT - 1
)
VREF
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