ADSP-BF607BBCZ-5 Datasheet, PDF (102/112 Pages) Analog Devices – Blackfin Dual Core Embedded Processor

ADSP-BF606/ADSP-BF607/ADSP-BF608/ADSP-BF609
Thermal Diode
The processor incorporates a thermal diode to monitor the die
temperature. The thermal diode is a grounded collector, PNP
Bipolar Junction Transistor (BJT). The SYS_TDA ball is con-
nected to the emitter and the SYS_TDK ball is connected to the
base of the transistor. These balls can be used by an external
temperature sensor (such as the ADM 1021A or the LM86 or
others) to read the die temperature of the chip.
The technique used by the external temperature sensor is to
measure the change in V_BE when the thermal diode is operated
at two different currents. This is shown in the following
equation:
V_BE=
n_Q

k_----T_-
q

In(N)


where:
n_Q = multiplication factor close to 1, depending on process
variations
k = Boltzmann’s constant
T = temperature (°Kelvin)
q = charge of the electron
N = ratio of the two currents
The two currents are usually in the range of 10 micro Amperes
to 300 micro Amperes for the common temperature sensor
chips available.
Table 69 contains the thermal diode specifications using the
transistor model. Note that Measured Ideality Factor already
takes into effect variations in beta (Β).
Table 69. Thermal Diode Parameters—Transistor Model
Symbol
Parameter
Min
Typ
Max
Unit
I_FW1
Forward Bias Current
10
300
A
I_E
n_Q2, ³
R_T2, ⁴
Emitter Current
Transistor Ideality
Series Resistance
10
300
A
1.006
2.8

1 _{Analog Devices does not recommend operation of the thermal diode under reverse bias.}
2 _{Not 100% tested. Specified by design characterization.}
3 _{The ideality factor, nQ, represents the deviation from ideal diode behavior as exemplified by the diode equation: IC = IS × (exp(qVBE/nQkT– 1), where IS = saturation current, ï€} 
q = electrical charge, V_BE = voltage across the diode, k = Boltzmann Constant, and T = absolute temperature (Kelvin).
4 _{The series resistance (RT) can be used for more accurate readings as needed.}
Rev. 0 | Page 102 of 112 | June 2013