Datasheet MAX6605 (Maxim) - 4

Low-Power Analog Temperature Sensor in SC70 Package Pin Description Applications Information PIN NAME FUNCTION Sensing Circuit Board and Ambient Temperatures
Supply Input. Decouple with a 0.1µF 1 VCC Temperature sensor ICs like the MAX6605 that sense capacitor to GND. their own die temperatures must be mounted on, or 2 A Must be connected to GND. close to, the object whose temperature they are intend- ed to measure. Because there is a good thermal path Temperature Sensor Output, 3 OUT between the SC70 package’s metal leads and the IC
MAX6605
CL ≥ 1nF die, the MAX6605 can accurately measure the temper- 4 B Must be connected to VCC. ature of the circuit board to which it is soldered. If the sensor is intended to measure the temperature of a heat- 5 GND Ground generating component on the circuit board, it should be
Detailed Description
mounted as close as possible to that component and should share supply and ground traces (if they are not The MAX6605 analog output temperature sensor’s out- noisy) with that component where possible. This will maxi- put voltage is a linear function of its die temperature. mize the heat transfer from the component to the sensor. The slope of the output voltage is 11.9mV/°C, and there The thermal path between the plastic package and the is a 744mV offset at 0°C to allow measurement of nega- die is not as good as the path through the leads, so the tive temperatures. The MAX6605 has three terminals: MAX6605, like all temperature sensors in plastic pack- VCC, GND, and OUT. The maximum supply current is ages, is less sensitive to the temperature of the surround- 10µA, and the supply voltage range is from +2.4V to ing air than it is to the temperature of its leads. It can be +5.5V for the -40°C to +105°C temperature range and successfully used to sense ambient temperature if the cir- +2.7V to +5.5V for the -55°C to +125°C temperature cuit board is designed to track the ambient temperature. range. The temperature error is <1°C at TA = +25°C, <3.8°C from TA = -20°C to +85°C, and <5.8°C from TA As with any IC, the wiring and circuits must be kept insu- = -55°C to +125°C. lated and dry to avoid leakage and corrosion, especially if the part will be operated at cold temperatures where con-
Nonlinearity
densation can occur. The benefit of silicon analog temperature sensors over The thermal resistance junction to ambient (θJA) is the thermistors is linearity over extended temperatures. The parameter used to calculate the rise of a device junction nonlinearity of the MAX6605 is typically 0.4°C over the temperature (TJ) due to its power dissipation. For the -20°C to +85°C temperature range. MAX6605, use the following equation to calculate the rise
Transfer Function
in die temperature: The temperature-to-voltage transfer function has an TJ = TA + θJA ((VCC x IQ) + (VCC - VOUT) IOUT) approximately linear positive slope and can be described by the equation: The MAX6605 is a very-low-power temperature sensor and is intended to drive very light loads. As a result, the VOUT = 744mV + (T ✕ 11.9mV/°C) temperature rise due to power dissipation on the die is where T is the MAX6605’s die temperature in °C. insignificant under normal conditions. For example, assume that the MAX6605 is operating from a +3V sup- Therefore: ply at +21.6°C (VOUT = 1V) and is driving a 100kΩ load (IOUT = 10µA). In the 5-pin SC70 package, the die tem- T (°C) = (VOUT - 744mV) / 11.9mV/°C perature will increase above the ambient by: To account for the small amount of curvature in the TJ - TA = θJA ((VCC x IQ) + (VCC - VOUT) IOUT) = transfer function, use the equation below to obtain a more accurate temperature reading: 324°C/W x ((3V x 10µA) + (3V - 1V) x 10µA) = 0.0162°C V Therefore, the error caused by power dissipation will be OUT = 0.744V + 0.0119V/°C ✕ T(°C) + negligible. 1.604 ✕ 10-6 V/°C2 ✕ (T(°C))2
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