ISL55112 Datasheet, PDF (13/20 Pages) Intersil Corporation – High-Speed Dual Precision CCD Driver

ISL55112
TABLE 1. ISL55112 DETAILED POWER DISSIPATION FORMULA/EXAMPLE (Continued)
FORMULA
VARIABLE
EXAMPLE
VALUES
UNIT
VARIABLES
SQUARED CALCULATIONS
NOTES
IH
6
mA
Stand By IH Current
Device Internal Capacitance
Log_Cint
3.5
pF
Per channel internal logic switching load
H1_Cint
60
pF
Effective Internal Driver Capacitance
H2_Cint
60
pF
Effective Internal Driver Capacitance
HL_Cint
6.3
pF
Effective Internal Driver Capacitance
RG_Cint
6.3
pF
Effective Internal Driver Capacitance
POWER DISSIPATION FORMULAS AND EXAMPLE CALCULATIONS
Wattage Sub Totals and Formula
Example Calculation
Standby Watts
H1_Logic_Watts
H2_Logic_Watts
HL_Logic_Watts
RG_Logic_Watts
H1_Cint_Watts
H2_Cint_Watts
HL_Cint_Watts
RG_Cint_Watts
H1_Cload_Watts
H2_Cload_Watts
HL_Cload_Watts
RG_Cload_Watts
=
VDD*IDD + H_DIFF*IH
=
Log_Cint*VDD² * H1_Freq
=
Log_Cint*VDD² * H2_Freq
=
Log_Cint*VDD² * HL_Freq
=
Log_Cint*VDD² * RG_Freq
=
H1_Cint*H_Diff² * H1_Freq
=
H2_Cint*H_Diff² * H2_Freq
=
HL_Cint*HL_Diff² * HL_Freq
=
RG_Cint*RG_Diff² * RG_Freq
=
H1_Cload*H_Diff² * H1_Freq
=
H2_Cload*H_Diff² * H2_Freq
=
HL_Cload*HL_Diff² * HL_Freq
=
RG_Cload*RG_Diff² * RG_Freq
0.0513
0.0015
0.0015
0.0015
0.0015
0.1536
0.1536
0.0161
0.0161
0.7680
0.7680
0.0563
0.0563
Total Watts
Total Watts
2.0455
T_JA
37
Degrees over ambient
75.68
Power Dissipation Notes
Power dissipation consists of 4 contributors:
1. Contributor 1 corresponds to the Standby Current of
the VDD Logic Supply (IDD) and VP-VN Driver Rails
(IH)
2. Contributor 2 corresponds to the dissipation from
running the H1, H2, RG and HL Inputs. Log_Cint
specifies the basis for the power consumed from the
VDD Supply for each input.
3. Contributor 3 corresponds to the Driver Rail Supply
dissipation due to internal capacitance. The value of
H1_Cint, H2_Cint, RG_Cint and HL_Cint correspond
to the effective internal capacitance of the drivers.
4. Contributor 4 corresponds to the Driver Rail Supply
dissipation due to load capacitance. The value of
H1_Cload, H2_Cload, RG_Cload and HL_Cload
correspond to the external capacitance of the device
being driven.
These are approximate formulae and the actual values
may be 15% to 20% off.
The maximum power dissipation allowed in a package is
determined according to Equation 1:
P_DMAX = ^T----^J---^M-----^A----^X--_Θ----^-_J---_A-^T----^A----^M----^A----^X--
(EQ. 1)
where:
• T_JMAX = Maximum junction temperature
• T_AMAX = Maximum ambient temperature
• θ_JA = Thermal resistance of the package
• P_DMAX = Maximum power dissipation in the package
The maximum power dissipation actually produced by an
IC is the total quiescent supply current times the total
power supply voltage, plus the power in the IC due to the
loads. Power also depends on number of channels
changing state and the frequency of operation. The
reader is cautioned against assuming the same level of
thermal performance in actual applications. A careful
inspection of conditions in your application should be
conducted. Great care must be taken to ensure Die
Temperature does not exceed +150°C Absolute Maximum
Thermal Limits.
13
FN6649.0
September 23, 2009