TPS61305YFFT Datasheet, PDF (66/77 Pages) Texas Instruments – 1.5A/4.1A Multiple LED Camera Flash Driver With I2CTM Compatible Interface

TPS61300
TPS61301
TPS61305, TPS61305A
SLVS957D – JUNE 2009 – REVISED OCTOBER 2012
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NTC SELECTION (TPS61305, TPS61305A, TPS61306)
The TPS61305/305A/306 requires a negative thermistor (NTC) for sensing the LED temperature. Once the
temperature monitoring feature is activated, a regulated bias current (c.a. 24μA) will be driven out of the TS port
and produce a voltage across the thermistor.
If the temperature of the NTC-thermistor rises due to the heat dissipated by the LED, the voltage on the TS input
pin decreases. When this voltage goes below the “warning threshold”, the LEDWARN bit in REGISTER6 is set.
This flag is cleared by reading the register.
If the voltage on the TS input decreases further and falls below “hot threshold”, the LEDHOT bit in REGISTER6
is set and the device goes automatically in shutdown mode to avoid damaging the LED. This status is latched
until the LEDHOT flag gets cleared by software.
The selection of the NTC-thermistor value strongly depends on the power dissipated by the LED and all
components surrounding the temperature sensor and on the cooling capabilities of each specific application. With
a 220kΩ (at 25°C) thermistor, the valid temperature window is set between 60°C to 90°C. The temperature
window can be enlarged by adding external resistors to the TS pin application circuit. In order to ensure proper
triggering of the LEDWARN and LEDHOT flags in noisy environments, the TS signal may require additional
filtering capacitance.
Figure 83. Temperature Monitoring Characteristic
Table 5. List of Negative Thermistor (NTC)
MANUFACTURER
MURATA
PART NUMBER
NCP18WM224J03RB
VALUE
220kΩ
66
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