Texas Instruments LMK01000 Evaluation Board LMK01000EVAL/NOPB LMK01000EVAL/NOPB 데이터 시트
제품 코드
LMK01000EVAL/NOPB
SNAS437G – FEBRUARY 2008 – REVISED OCTOBER 2009
CURRENT CONSUMPTION / POWER DISSIPATION CALCULATIONS (Vcc = 3.3 V, T
A
= 25° C)
Current
Power
Power
Consumption
Dissipated in
Block
Condition
Dissipated in
at 3.3 V
LVPECL emitter
device (mW)
(mA)
resistors (mW)
Core Current
All outputs disabled. Includes input buffer currents.
19
62.7
-
Low clock buffer The low clock buffer is enabled anytime one of CLKout0 through
9
29.7
-
(internal)
CLKout3 are enabled
High clock
The high clock buffer is enabled anytime one of the CLKout4
9
29.7
-
buffer (internal)
through CLKout7 are enabled
LVDS output, Bypassed mode
17.8
58.7
-
LVPECL output, Bypassed mode
40
72
60
(includes 120
Ω
emitter resistors)
Output buffers
LVPECL output, disabled mode
17.4
38.3
19.1
(includes 120
Ω
emitter resistors)
LVPECL output, disabled mode.
0
0
-
No emitter resistors placed; open outputs
Additional current per channel due
LVPECL Output
0.5
1.65
-
Vboost
to setting Vboost from 0 to 1.
LVDS Output
1.5
5.0
Divide enabled, divide = 2
5.3
17.5
-
Divide circuitry
per output
per output
Divide enabled, divide > 2
8.5
28.0
-
Delay enabled, delay < 8
5.8
19.1
-
Delay circuitry
per output
per output
Delay enabled, delay > 7
9.9
32.7
-
Entire device
LMK01000
85.8
223.1
60
CLKout0 &
LMK01010
63.6
209.9
-
CLKout4
enabled in
enabled in
LMK01020
108
236.4
120
Bypassed mode
Entire device
LMK01000
323.8
768.5
300
all outputs
LMK01010
212.8
702.3
-
enabled with no
delay and divide
delay and divide
LMK01020
390.4
808.3
480
value of 2
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 Bypassed 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 emitter current, but some of the
power from the current draw is dissipated in the external 120
device with 1 LVDS (CLKout0) & 1 LVPECL (CLKout4) output in Bypassed 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 emitter 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.
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 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) operating 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)
minus the power dissipated in any emitter resistors connected to any of 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) operating 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)
2
/ 120
Ω
= 30 mW. When the LVPECL output is disabled, the emitter resistor voltage is
~1.07 V. Therefore the power dissipated in each emitter resistor is approximately (1.07 V)
2
/ 120
Ω
= 9.5 mW.
THERMAL MANAGEMENT
Power consumption of the LMK01000 family device can be high enough to require attention to thermal
management. For reliability and performance reasons the die temperature should be limited to a maximum of
125 °C. That is, as an estimate, T
management. For reliability and performance reasons the die temperature should be limited to a maximum of
125 °C. That is, as an estimate, T
A
(ambient temperature) plus device power consumption times
θ
JA
should not
exceed 125 °C.
Copyright © 2008–2009, Texas Instruments Incorporated
15
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