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8536CGI-33LF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19
REVISION B 7/10/15
8536I-33 DATA SHEET
13 LOW SKEW, 1-TO-6, CRYSTAL OSCILLATOR/LVCMOS-TO-
3.3V, 2.5V LVPECL/LVCMOS FANOUT BUFFER
POWER CONSIDERATIONS
This section provides information on power dissipation and junction temperature for the 8536I-33.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the 8536I-33 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V
CC
= 3.3V + 5% = 3.465V, which gives worst case results.
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
Core and LVPECL Output Power Dissipation
• Power (core)
MAX
= V
CC_MAX
* I
EE_MAX
= 3.465V * 80mA = 277.2mW
• Power (outputs)
MAX
= 30mW/Loaded Output pair
If all outputs are loaded, the total power is 3 * 30mW = 90mW
LVCMOS Output Power Dissipation
• Output Impedance R
OUT
Power Dissipation due to Loading 50Ω to V
CCO_LVCMOS
/2
Output Current I
OUT
= V
CCO_MAX
/ [2 * (50Ω + R
OUT
)] = 3.465V / [2 * (50Ω + 15Ω] = 26.7mA
• Power Dissipation on the R
OUT
per LVCMOS output
Power (R
OUT
) = R
OUT
* (I
OUT
)
2
= 15Ω * (26.7mA)
2
= 10.7mW per output
• Total Power Dissipation on the R
OUT
Total Power (R
OUT
) = 10.7mW * 3 = 32.1mW
Total Power Dissipation
• Total Power
= Power (LVPECL) + Total Power (R
OUT
)
= 277.2mW + 90mW + 32.1mW
= 399.3mW
LOW SKEW, 1-TO-6, CRYSTAL OSCILLATOR/LVCMOS-TO-
3.3V, 2.5V LVPECL/LVCMOS FANOUT BUFFER
8536I-33 DATA SHEET
14 REVISION B 7/10/15
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad and directly affects the reliability of the
device. The maximum recommended junction temperature for HiPerClockS
TM
devices is 125°C.
The equation for Tj is as follows: Tj = θJA * Pd_total + TA
Tj = Junction Temperature
θ
JA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
T
A
= Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ
JA
must be used. Assuming no air fl ow
and a multi-layer board, the appropriate value is 91.1°C/W per Table 7 below.
Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:
85°C + 0.3993W * 91.1°C/W = 121.4°C. This is below the limit of 125°C.
This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air fl ow,
and the type of board (single layer or multi-layer).
TABLE 7. THERMAL RESISTANCE θ
JA
FOR 20-PIN TSSOP, FORCED CONVECTION
θ
JA
by Velocity (Linear Feet per Minute)
0 200 500
Multi-Layer PCB, JEDEC Standard Test Boards 91.1°C/W 86.7°C/W 84.6°C/W
REVISION B 7/10/15
8536I-33 DATA SHEET
15 LOW SKEW, 1-TO-6, CRYSTAL OSCILLATOR/LVCMOS-TO-
3.3V, 2.5V LVPECL/LVCMOS FANOUT BUFFER
3. Calculations and Equations.
The purpose of this section is to derive the power dissipated into the load.
LVPECL output driver circuit and termination are shown in Figure 6.
To calculate worst case power dissipation into the load, use the following equations which assume a 50Ω load, and a termination
voltage of V
CCO
– 2V.
• For logic high, V
OUT
= V
OH_MAX
= V
CCO_MAX
– 0.9V
(V
CCO_MAX
– V
OH_MAX
)
= 0.9V
• For logic low, V
OUT
= V
OL_MAX
= V
CCO_MAX
– 1.7V
(V
CCO_MAX
– V
OL_MAX
)
= 1.7V
Pd_H is power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = [(V
OH_MAX
– (V
CCO_MAX
– 2V))/R
L
] * (V
CCO_MAX
– V
OH_MAX
) = [(2V
– (V
CC_MAX
– V
OH_MAX
))
/R
L
] * (V
CC_MAX
– V
OH_MAX
) =
[(2V
– 0.9V)/50Ω] * 0.9V = 19.8mW
Pd_L = [(V
OL_MAX
– (V
CCO_MAX
– 2V))/R
L
] * (V
CCO_MAX
– V
OL_MAX
) = [(2V
– (V
CCO_MAX
– V
OL_MAX
))
/R
L
] * (V
CCO_MAX
– V
OL_MAX
) =
[(2V
– 1.7V)/50Ω] * 1.7V = 10.2mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 30mW
FIGURE 6. LVPECL DRIVER CIRCUIT AND TERMINATION
V
OUT
V
CCO
V
CCO
-
2V
Q1
RL
50Ω
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19

8536CGI-33LF

Mfr. #:
Buy 8536CGI-33LF
Manufacturer:
IDT
Description:
Clock Drivers & Distribution 6 LVCMOS OUT BUFFER
Lifecycle:
New from this manufacturer.
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