Datasheet

LTC6993-1/LTC6993-2
LTC6993-3/LTC6993-4
19
69931234fb
APPLICATIONS INFORMATION
Table 2. Typical Supply Current
CONDITION TYPICAL I
S(IDLE)
TYPICAL ∆I
S(ACTIVE)
*
N
DIV
≤ 64
V
+
• N
DIV
• 7pF + 4pF
( )
t
OUT
+
V
+
500kΩ
+ 2.2 •I
SET
+ 50µA
V
+
•
Duty Cycle
t
OUT
• N
DIV
• 5pF + 18pF + C
LOAD
( )
N
DIV
≥ 512
V
+
•N
DIV
• 7pF
t
OUT
+
V
+
500kΩ
+ 1.8 •I
SET
+ 50µA
V
+
•
Duty Cycle
t
OUT
• C
LOAD
*Ignoring resistive loads (assumes R
LOAD
= ∞)
Power Supply Current
The Electrical Characteristics table specifies the supply
current while the part is idle (waiting to be triggered).
I
S(IDLE)
varies with the programmed t
OUT
and the supply
voltage. Once triggered, the instantaneous supply current
increases to I
S(ACTIVE)
while the timing circuit is active.
I
S(ACTIVE)
= I
S(IDLE)
+ ∆I
S(ACTIVE)
The average increase in supply current ∆I
S(ACTIVE)
de-
pends on the output duty cycle (or negative duty cycle,
if POL
= 1), since that represents the percentage of time
that the circuit is active. I
S(IDLE)
and ∆I
S(ACTIVE)
can be
estimated using the equations in Table 2.
Figure 12 shows how the supply current increases from
I
S(IDLE)
as the input frequency increases. The increase is
smaller at higher N
DIV
settings.
DUTY CYCLE (%)
IDLE
POWER SUPPLY CURRENT (µA)
150
200
250
80
69931234 F12
100
50
0
20
40
60
100
V
+
= 3.3V
DUTY CYCLE = f
IN
• t
OUT
÷1, R
SET
= 50k
÷8, R
SET
= 50k
÷1, R
SET
= 100k
÷1, R
SET
= 800k
C
LOAD
= 5pF
R
LOAD
= ∞
Figure 12. I
S(ACTIVE)
vs Output Duty Cycle