
REF19x Series
APPLICATIONS 
OUTPUT SHORT-CIRCUIT BEHAVIOR 
The REF19x family of devices is completely protected from 
damage due to accidental output shorts to GND or to V
+
. In the 
event of an accidental short-circuit condition, the reference 
device shuts down and limits its supply current to 40 mA. 
Rev. I | Page 19 of 28 
V
+
V
OUT
SLEEP (SHUTDOWN)
GND
0
Figure 20. Simplified Schematic 
DEVICE POWER DISSIPATION CONSIDERATIONS 
The REF19x family of references is capable of delivering load 
currents to 30 mA with an input voltage that ranges from  
3.3 V to 5 V. When these devices are used in applications with 
large input voltages, exercise care to avoid exceeding the 
maximum internal power dissipation of these devices. 
Exceeding the published specifications for maximum power 
dissipation or junction temperature can result in premature 
device failure. The following formula should be used to 
calculate a device’s maximum junction temperature or 
dissipation: 
T
T
P
θ
JA
A
J
D
=
In this equation, T
J
 and T
A
 are the junction and ambient 
temperatures, respectively; P
D
 is the device power dissipation; 
and θ
JA
 is the device package thermal resistance. 
OUTPUT VOLTAGE BYPASSING 
For stable operation, low dropout voltage regulators and 
references generally require a bypass capacitor connected from 
their V
OUT
 pins to their GND pins. Although the REF19x family 
of references is capable of stable operation with capacitive loads 
exceeding 100 μF, a 1 μF capacitor is sufficient to guarantee 
rated performance. The addition of a 0.1 μF ceramic capacitor 
in parallel with the bypass capacitor improves load current 
transient performance. For best line voltage transient 
performance, it is recommended that the voltage inputs of these 
devices be bypassed with a 10 μF electrolytic capacitor in 
parallel with a 0.1 μF ceramic capacitor. 
SLEEP MODE OPERATION 
All REF19x devices include a sleep capability that is 
TTL/CMOS-level compatible. Internally, a pull-up current 
source to V
IN
 is connected at the SLEEP pin. This permits the 
SLEEP pin to be driven from an open collector/drain driver. A 
logic low or a 0 V condition on the SLEEP pin is required to 
turn off the output stage. During sleep, the output of the 
references becomes a high impedance state where its potential 
would then be determined by external circuitry. If the sleep 
feature is not used, it is recommended that the SLEEP pin be 
connected to V
IN
 (Pin 2). 
BASIC VOLTAGE REFERENCE CONNECTIONS 
The circuit in Figure 21 illustrates the basic configuration for 
the REF19x family of references. Note the 10 μF/0.1 μF bypass 
network on the input and the 1 μF/0.1 μF bypass network on 
the output. It is recommended that no connections be made to 
Pin 1, Pin 5, Pin 7, and Pin 8. If the sleep feature is not required, 
Pin 3 should be connected to V
IN
. 
NC
NC
OUTPUT
V
IN
SLEEP
NC
NC
0.1μF
10μF
REF19x
NC = NO CONNECT
8
7
6
5
1
2
3
4
1μF
TANT
0.1μF
+
0
Figure 21. Basic Voltage Reference Configuration 
MEMBRANE SWITCH-CONTROLLED POWER 
SUPPLY 
With output load currents in the tens of mA, the REF19x family 
of references can operate as a low dropout power supply in 
hand-held instrument applications. In the circuit shown in 
Figure 22, a membrane on/off switch is used to control the 
operation of the reference. During an initial power-on condition, 
the SLEEP pin is held to GND by the 10 kΩ resistor. Recall that 
this condition (read: three-state) disables the REF19x output. 
When the membrane on switch is pressed, the SLEEP pin is 
momentarily pulled to V
IN
, enabling the REF19x output. At this 
point, current through the 10 kΩ resistor is reduced, and the 
internal current source connected to the SLEEP pin takes 
control. Pin 3 assumes and remains at the same potential as V
IN
. 
When the membrane off switch is pressed, the SLEEP pin is 
momentarily connected to GND, which once again disables the 
REF19x output.