LTC6991HS6#TRMPBF Linear Technology, LTC6991HS6#TRMPBF Datasheet - Page 14

• Manufacturer Part Number: LTC6991HS6#TRMPBF
• Description: IC TIMERBLOX OSCILLATOR TSOT23-6
• Manufacturer: Linear Technology

Specifications of LTC6991HS6#TRMPBF

• Frequency: *
• Voltage - Supply: *
• Current - Supply: 135µA
• Operating Temperature: *
• Package / Case: TSOT-23-6, TSOT-6
• Count: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LTC6991HS6#TRMPBFTR

LTC6991
applicaTions inForMaTion
Basic Operation
The simplest and most accurate method to program the
LTC6991 is to use a single resistor, R
and GND pins. The design procedure is a 3-step process.
First select the POL bit setting and N
the value for the R
Step 1: Select the POL Bit Setting
The LTC6991 can operate in normal (active-high) or inverted
(active-low) modes, depending on the setting of the POL
bit. The best choice depends on the the application.
Step 2: Select the N
As explained earlier, the voltage on the DIV pin sets the
DIVCODE which determines both the POL bit and the
N
be selected to be within the following range.
To minimize supply current, choose the lowest N
(generally recommended). Alternatively, use Table 1
as a guide to select the best N
application.
With POL already chosen, this completes the selection of
DIVCODE. Use Table 1 to select the proper resistor divider
or V
Step 3: Calculate and Select R
The final step is to calculate the correct value for R
using the following equation.
Select the standard resistor value closest to the calculated
value.

DIV
R
16 384
DIV
SET
value. For a given output clock period, N
.
t
OUT
/V
=
+
ms
1 024
ratio to apply to the DIV pin.
.
50
≤
N
k
ms
DIV
SET
•
DIV
≤
N
t
resistor.
OUT
1 024
DIV
Frequency Divider Value
.
t
OUT
ms
SET
DIV
DIV
SET
value for the given
value, then calculate
, between the SET
DIV
DIV
should
value
SET
(1)
(2)
Example: Design a 1Hz oscillator with minimum power
consumption and active-high reset input.
Step 1: Select the POL Bit Setting
For noninverted (active-high) functionality, choose
POL = 0.
Step 2: Select the N
Choose an N
Equation (1), using t
Potential settings for N
is the best choice, as it minimizes supply current by us-
ing a large R
DIVCODE = 2. Using Table 1, choose R1 = 976k and
R2 = 182k values to program DIVCODE = 2.
Step 3: Select R
Calculate the correct value for R
Since 763k is not available as a standard 1% resistor,
substitute 768k if a –0.7% frequency shift is acceptable.
Otherwise, select a parallel or series pair of resistors such
as 576k + 187k to attain a more precise resistance.
The completed design is shown in Figure 11.
61.04 ≤ N
R
SET
=
RST
1 024
R
763k
.
DIV
SET
SET
50
DIV
k
≤ 976.6
RST
GND
SET
resistor. POL = 0 and N
SET
ms
Figure 11. 1Hz Oscillator
value that meets the requirements of
LTC6991
•
DIV
OUT
1000
DIV
OUT
DIV
Frequency Divider Value
V
= 1000ms:
64
+
include 64 and 512. N
ms
=
2.25V TO 5.5V
SET
763
using Equation (2).
k
R1
976k
DIVCODE = 2
R2
182k
6991 F11
DIV
= 64 requires
DIV
= 64
6991f