LTC6990CDCB#TRMPBF Linear Technology, LTC6990CDCB#TRMPBF Datasheet - Page 10

• Manufacturer Part Number: LTC6990CDCB#TRMPBF
• Description: IC MPU SUPERVISORY 6DFN
• Manufacturer: Linear Technology

Specifications of LTC6990CDCB#TRMPBF

• Frequency: *
• Voltage - Supply: *
• Current - Supply: 235µA
• Operating Temperature: *
• Package / Case: 6-WFDFN Exposed Pad
• Count: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LTC6990CDCB#TRMPBFTR

OPERATION
LTC6990
The LTC6990 is built around a master oscillator with a
1MHz maximum frequency. The oscillator is controlled
by the SET pin current (I
1MHz • 50k conversion factor that is accurate to ±0.8%
under typical conditions.
A feedback loop maintains V
as the primary means of controlling the output frequency.
The simplest way to generate I
(R
The master oscillator equation reduces to:
From this equation it is clear that V
the output frequency when using a single program resistor
(R
inherent frequency accuracy Δf
R
between 1.25μA and 20μA) produce the best results,
although R
reduced accuracy.
The LTC6990 includes a programmable frequency divider
which can further divide the frequency by 1, 2, 4, 8, 16,
32, 64 or 128 before driving the OUT pin. The divider ratio
N
With R
10
SET
DIV
SET
SET
f
f
f
f
OUT
OUT
MASTER
MASTER
is set by a resistor divider attached to the DIV pin.
) between SET and GND, such that I
). Error sources are limited to R
values between 50k and 800k (equivalent to I
SET
=
=
t
t
in place of V
OUT
SET
OUT
1
=
1
=
t
t
may be reduced to 25k (I
MASTER
=
MASTER
=
1MHz • 50k
N
1MHz • 50k
1
1
DIV
N
• R
DIV
SET
=
= 1MHz • 50k •
SET
SET
1MHz • 50k
/I
SET
SET
) and voltage (V
R
•
SET
SET
OUT
at 1V ±30mV, leaving I
V
the equation reduces to:
I
SET
SET
is to connect a resistor
SET
of the LTC6990.
SET
drift will not affect
V
tolerance and the
I
SET
SET
SET
SET
= 40μA) with
= V
SET
SET
), with a
/R
SET
SET
SET
.
DIVCODE
The DIV pin connects to an internal, V
A/D converter that monitors the DIV pin voltage (V
determine the DIVCODE value. DIVCODE programs two
settings on the LTC6990:
1. DIVCODE determines the output frequency divider
2. DIVCODE determines the state of the output when
V
and GND as shown in Figure 1.
DIV
setting, N
disabled, via the Hi-Z bit.
may be generated by a resistor divider between V
Figure 1. Simple Technique for Setting DIVCODE
DIV
.
LTC6990
GND
6990 F01
DIV
V
+
2.25V TO 5.5V
R1
R2
+
referenced 4-bit
DIV
) to
6990f
+