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
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