LMK01000ISQ NSC [National Semiconductor], LMK01000ISQ Datasheet - Page 15

• Manufacturer Part Number: LMK01000ISQ
• Description: 1.6 GHz High Performance Clock Buffer, Divider, and Distributor
• Manufacturer: NSC [National Semiconductor]

3.2 CURRENT CONSUMPTION / POWER DISSIPATION
CALCULATIONS ( Vcc = 3.3 V, T
From the above table, the current can be calculated in any
configuration. For example, the current for the entire device
with 1 LVDS (CLKout0) & 1 LVPECL (CLKout4) output in By-
passed mode can be calculated by adding up the following
blocks: core current, low clock buffer, high clock buffer, one
LVDS output buffer current, and one LVPECL output buffer
current. There will also be one LVPECL output drawing emit-
ter current, but some of the power from the current draw is
dissipated in the external 120 Ω resistors which doesn't add
to the power dissipation budget for the device. If delays or
divides are switched in, then the additional current for these
stages needs to be added as well.
For power dissipated by the device, the total current entering
the device is multiplied by the voltage at the device minus the
power dissipated in any emitter resistors connected to any of
Block
Core Current
Low clock buffer
(internal)
High clock
buffer (internal)
Output buffers
Vboost
Divide circuitry
per output
Delay circuitry
per output
Entire device
CLKout0 &
CLKout4
enabled in
Bypassed mode
Entire device
all outputs
enabled with no
delay and divide
value of 2
Condition
All outputs disabled. Includes input buffer currents.
The low clock buffer is enabled anytime one of CLKout0
through CLKout3 are enabled
The high clock buffer is enabled anytime one of the CLKout4
through CLKout7 are enabled
LVDS output, Bypassed mode
LVPECL output, Bypassed mode
(includes 120 Ω emitter resistors)
LVPECL output, disabled mode
(includes 120 Ω emitter resistors)
LVPECL output, disabled mode.
No emitter resistors placed; open outputs
Additional current per channel due
to setting Vboost from 0 to 1.
Divide enabled, divide = 2
Divide enabled, divide > 2
Delay enabled, delay < 8
Delay enabled, delay > 7
LMK01000
LMK01010
LMK01020
LMK01000
LMK01010
LMK01020
A
= 25° C )
LVPECL Output
LVDS Output
15
the LVPECL outputs. If no emitter resistors are connected to
the LVPECL outputs, this power will be 0 watts. For example,
in the case of 1 LVDS (CLKout0) & 1 LVPECL (CLKout4) op-
erating at 3.3 volts for LMK01000, we calculate 3.3 V × (10 +
9 + 9 + 17.8 + 40) mA = 3.3 V × 85.8 mA = 283.1 mW. Because
the LVPECL output (CLKout4) has the emitter resistors
hooked up and the power dissipated by these resistors is 60
mW, the total power dissipation is 283.1 mW - 60 mW = 223.1
mW. When the LVPECL output is active, ~1.9 V is the average
voltage on each output as calculated from the LVPECL Voh
& Vol typical specification. Therefore the power dissipated in
each emitter resistor is approximately (1.9 V)
mW. When the LVPECL output is disabled, the emitter resis-
tor voltage is ~1.07 V. Therefore the power dissipated in each
emitter resistor is approximately (1.07 V)
Consumptio
n at 3.3 V
Current
323.8
212.8
390.4
(mA)
17.8
17.4
85.8
63.6
108
0.5
1.5
5.3
8.5
5.8
9.9
19
40
9
9
0
Dissipated
in device
Power
(mW)
223.1
209.9
236.4
768.5
702.3
808.3
62.7
29.7
29.7
58.7
38.3
1.65
17.5
28.0
19.1
32.7
5.0
72
0
2
/ 120 Ω = 9.5 mW.
LVPECL emitter
resistors (mW)
Dissipated in
2
/ 120 Ω = 30
Power
www.national.com
19.1
120
300
480
60
60
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