ltc6992-2-ltc6992-3 Linear Technology Corporation, ltc6992-2-ltc6992-3 Datasheet - Page 15

• Manufacturer Part Number: ltc6992-2-ltc6992-3
• Description: Timerblox Voltage-controlled Pulse Width Modulator Pwm
• Manufacturer: Linear Technology Corporation

OPERATION
Table 1. DIVCODE Programming
Table 1 offers recommended 1% resistor values that ac-
curately produce the correct voltage division as well as the
corresponding N
resistor pairs. Other values may be used as long as:
1. The V
2. The driving impedance (R1||R2) does not exceed 500kΩ.
If the voltage is generated by other means (i.e. the output
of a DAC) it must track the V
tor tolerances and temperature effects).
DIVCODE
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
DIV
/V
+
ratio is accurate to ±1.5% (including resis-
DIV
POL
and POL values for the recommended
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0.001
1000
0.01
100
0.1
10
1
0V
0
+
16384
16384
supply voltage. The last
1024
4096
4096
1024
N
256
256
1
16
64
64
16
DIV
1
4
4
1
Figure 2. Frequency Range and POL Bit vs DIVCODE
2
POL BIT = 0
3
4
RECOMMENDED f
3.906kHz to 62.5kHz
976.6Hz to 15.63kHz
244.1Hz to 3.906kHz
244.1Hz to 3.906kHz
976.6Hz to 15.63kHz
3.906kHz to 62.5kHz
15.63kHz to 250kHz
15.63kHz to 250kHz
61.04Hz to 976.6Hz
15.26Hz to 244.1Hz
3.815Hz to 61.04Hz
3.815Hz to 61.04Hz
15.26Hz to 244.1Hz
61.04Hz to 976.6Hz
62.5kHz to 1MHz
62.5kHz to 1MHz
5
6
INCREASING V
7
0.5• V
OUT
+
8
column in Table 1 shows the ideal ratio of V
supply voltage, which can also be calculated as:
For example, if the supply is 3.3V and the desired DIVCODE
is 4, V
Figure 2 illustrates the information in Table 1, showing
that N
DIV
9
V
V
DIV
+
DIV
DIV
10
R1 (kΩ)
POL BIT = 1
=
Short
Open
1000
1000
1000
1000
1000
is symmetric around the DIVCODE midpoint.
= 0.281 • 3.3V = 928mV ± 50mV.
976
976
887
681
523
392
280
182
102
LTC6992-1/LTC6992-2/
11
DIVCODE + 0.5
LTC6992-3/LTC6992-4
12
16
13
14
R2 (kΩ)
Short
Open
1000
1000
1000
1000
1000
102
182
280
392
523
681
887
976
976
6992 F02
15
±1.5%
V
+
≤0.03125 ±0.015
≥0.96875 ±0.015
0.09375 ±0.015
0.15625 ±0.015
0.21875 ±0.015
0.28125 ±0.015
0.34375 ±0.015
0.40625 ±0.015
0.46875 ±0.015
0.53125 ±0.015
0.59375 ±0.015
0.65625 ±0.015
0.71875 ±0.015
0.78125 ±0.015
0.84375 ±0.015
0.90625 ±0.015
V
DIV
/V
DIV
+
15
69921234fb
to the