TCN4040 Datasheet, PDF (4/9 Pages) TelCom Semiconductor, Inc – PRECISION MICROPOWER SHUNT VOLTAGE REFERENCE

PRELIMINARY INFORMATION
PRECISION MICROPOWER
SHUNT VOLTAGE REFERENCE
TCN4040
APPLICATIONS INFORMATION
Available in a space saving SOT-23B-3 surface mount
package, the TCN4040 is a precision micro-power curva-
ture-corrected bandgap shunt voltage reference. The
TCN4040 is designed for stable operation without an exter-
nal capacitor connected between the “+” pin and the “–” pin.
The TCN4040 also remains stable, however, if a bypass
capacitor is used. The minimum operating current increase
is 60mA and the maximum operating current is 15mA.
The TCN4040, in the SOT-23B-3 package has a para-
sitic Schottky diode between pin 3 (–) and pin 1. (Die attach
interface contact). Therefore, pin 1 of the SOT-23B-3 pack-
age must be left floating or connected to pin 3.
In a conventional shunt regulator application, an exter-
nal series resistor (R_S) is connected between the supply
voltage and the TCN4040 (Figure 1). R_S determines the
current that flows through the load (I_L) and the TCN4040
(I_Q). Even when the supply voltage is at its minimum, and
the load current is at its maximum value, R_S should be small
enough to supply at least the minimum acceptable I_Q to the
TCN4040 since load current and supply voltage may vary.
Conversely, when the supply voltage is at its maximum and
I_L is at its minimum, R_S should be large enough that the
current flowing through the TCN4040 is less than 15mA.
R_S is determined by the supply voltage, (V_S), the load
and operating current, (I_L and I_Q), and the TCN4040’s
reverse breakdown voltage, V_R.
V_S – V_R
R_S =
I_L + I_Q
V_S
R_S
I_Q + I_L
V_R
I_L
I_Q
TCN4040
Figure 1. Shunt Regulator
TCN4040-01 6/16/97
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