LM122 National Semiconductor, LM122 Datasheet - Page 5

• Manufacturer Part Number: LM122
• Description: Precision Timers
• Manufacturer: National Semiconductor

Functional Diagram
Timing Diagram
Pin Function Description
One of the main features of the LM122 is its great versatility
Since this device is unique a description of the functions
and limitations of each pin is in order This will make it much
easier to follow the discussion of the various applications
presented in this note
V
ing a single supply this terminal may be driven by any volt-
age between 4 5V and 40V The effect of supply variations
on timing period is less than 0 005% V so supplies with
high ripple content may be used without causing pulse width
changes Supply bypassing on V
but may be necessary when driving highly reactive loads
a
is the positive supply terminal of the LM122 When us-
a
is not generally needed
5
Quiescent current drawn from the V
2 5 mA independent of the supply voltage Of course addi-
tional current will be drawn if the reference is externally
loaded
The V
enced to the ground pin Up to 5 0 mA can be drawn from
this pin for driving external networks In most applications
the timing resistor is tied to V
situations where a more linear charging current is required
The regulated voltage is very useful in applications where
the LM122 is not used as a timer such as switching regula-
tors variable reference comparators and temperature con-
REF
pin is the output of a 3 15V series regulator refer-
REF
a
but it need not be in
terminal is typically
TL H 7768 – 10
TL H 7768– 9