MC34708VK View Datasheet(PDF) - Freescale Semiconductor
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MC34708VK Datasheet PDF : 159 Pages
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General Product Characteristics
5.2.1 Power Dissipation
During operation, the temperature of the die should not exceed the maximum junction temperature. To optimize the thermal
management scheme and avoid overheating, the MC34708 PMIC provides a thermal management system. The thermal
protection is based on a circuit with a voltage output proportional to the absolute temperature.This voltage can be read out via
the ADC for specific temperature readouts, see Channel 3 Die Temperature.
The ADEN SPI bit must be set = 1 to enable the comparators for the thermal monitoring (THERM110, THERM120, THERM125,
THERM130, and thermal shutdown). With ADEN = 0 the thermal monitors and thermal shutdown are disabled. Interrupts
THERM110, THERM120, THERM125, and THERM130 will be generated when respectively crossing in either direction the
thresholds specified in Table 6. The temperature range can be determined by reading the THERMxxxS bits.
Thermal protection is integrated to power off the MC34708 PMIC and disables the charger circuitry in case of over dissipation.
This thermal protection will act above the maximum junction temperature to avoid any unwanted power downs. The protection is
debounced for 8.0 ms in order to suppress any (thermal) noise. This protection should be considered as a fail-safe mechanism
and therefore the application design should be dimensioned such that this protection is not tripped under normal conditions. The
temperature thresholds and the sense bit assignment are listed in Table 6
.
Table 6. Thermal Protection Thresholds
Parameter
Min
Typ
Max
Units
Notes
Thermal 110 °C threshold (THERM110)
Thermal 120 °C threshold (THERM120)
Thermal 125 °C threshold (THERM125)
Thermal 130 °C threshold (THERM130)
Thermal warning hysteresis
Thermal protection threshold
105
110
115
115
120
125
120
125
130
125
130
135
2.0
-
4.0
130
140
150
°C
°C
°C
°C
°C
(12)
°C
Notes
12. Equivalent to approx. 30 mW min, 60 mW max
The THERM1xx thresholds are debounced by the SPI bits DIE_TEMP_DB[1:0], which are programmable from 100 s to 4.0 ms
(4.0 ms by default), see Table 7. When the die temperature crosses these thresholds, the corresponding sense bit will change
and an interrupt will be generated to notify the software that the hardware is reaching its thermal limit.
Table 7. Die Temp Debounce Settings
DIE_TEMP_DB [1:0]
Time
00
0.100
01
1.0
10
2.5
11 (default)
4.0
Units
ms
ms
ms
ms
Analog Integrated Circuit Device Data
Freescale Semiconductor
MC34708
16
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