Datasheet

LTC6902
5
6902f
Output Operating at 20MHz,
V
S
= 5V
1V/DIV
12.5ns/DIV
69012 G06
1V/DIV
25ns/DIV
69012 G07
V
+
= 5V, R
SET
= 10k, C
L
= 10pF
V
+
= 3V, R
SET
= 20k, C
L
= 10pF
Output Operating at 10MHz,
V
S
= 3V
0V
0V
TYPICAL PERFOR A CE CHARACTERISTICS
UW
QUICK DESIG GUIDE
U
Step 1. Select Multiphase Mode, Setting M
By selecting the multiphase mode, a division parameter M
is also chosen:
2-Phase: Connect PH Pin to GND M = 1
3-Phase: Leave PH Open M = 3
4-Phase: Connect PH Pin to V+ M = 4
Step 2. Choosing Programmable Divider Setting N
A. For applications using spread spectrum frequency
modulation (SSFM) or applications that are constant fre-
quency where low clock jitter is the primary specification:
DIVIDER SETTING FREQUENCY RANGE (f
OUT
• M)
N = 1 Connect DIV Pin to GND 2MHz to 20MHz
N = 10 Leave DIV Open 200kHz to 2MHz
N = 100 Connect DIV Pin to V
+
<200kHz
Note: The frequency range numbers are for a 5V supply where a 20MHz
output is the maximum frequency supported. For low supply applications
(2.7V ≤ V
+
≤ 4V), the maximum rated output frequency is 10MHz and all
of the above numbers should be halved.
B. For constant frequency applications where frequency
accuracy is the primary specification:
DIVIDER SETTING FREQUENCY RANGE (f
OUT
• M)
N = 1 Connect DIV Pin to GND > 500kHz*
N = 10 Leave DIV Open 50kHz to 500kHz
N = 100 Connect DIV Pin to V
+
<50kHz
*The maximum frequency (f
OUT
• M) is 20MHz for 5V applications and is
10MHz for low supply applications (2.7V ≤ V
+
≤ 4V).
f
MHz
NM
k
R
kHz f MHz
SpreadingPercentage
R
R
OUT
SET
OUT
SET
MOD
=•
Ω






≤≤
=
10 20
520
20
•
•
;
V
+
DIV
PH
OUT1
OUT2
OUT4
OUT3
OUT2
OUT1
SET
MOD
GND
OUT4
OUT3
LTC6902
R
SET
R
MOD
V
+
DIV
PH
6902 F01
0.1µF
Figure 1. Typical Application with Design Equation