TC3405 Datasheet, PDF (5/16 Pages) Microchip Technology – 16-Bit, Low Cost, Low Power Sigma-Delta A/D Converter

TC3405
2.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1: PIN FUNCTION TABLE
Pin No.
(16-Pin PDIP) Symbol
(16-Pin QSOP)
Description
1
IN1+ Analog Input. This is the positive terminal of a true differential input consisting of IN1+ and IN1-.
V_IN1 = (IN1+ – IN-). See Section 1.0, Electrical Characteristics.
2
IN1- Analog Input. This is the negative terminal of a true differential input consisting of IN1+ and IN1-.
V_IN1 = (IN+ – IN-) IN1- can swing to, but not below, ground. See Section 1.0, Electrical Characteristics.
3
IN2 Analog Input. This is the positive terminal of a true differential input with the negative input tied
internally to GND. See Section 1.0, Electrical Characteristics.
4
IN3 Analog Input. This is the positive terminal of a true differential input with the negative input tied
internally to GND. See Section 1.0, Electrical Characteristics.
5
IN4 Analog Input. This is the positive terminal of a true differential input with the negative input tied
internally to GND. See Section 1.0, Electrical Characteristics.
6
V_TH Analog Input. This is the positive input to the internal comparator used to monitor the voltage supply.
The negative input is tied to an internal reference. When V_TH falls below the internal reference, the
reset generator drives RESET low. See Section 1.0, Electrical Characteristics.
7
REF_IN Analog Input. The converter’s reference voltage is the differential between this pin and ground times
two. It may be tied directly to REF_OUT or scaled using a resistor divider. Any user supplied
reference voltage less than 1.25 may be used in place of REF_OUT.
8
GND Ground Terminal.
9
REF_OUT Analog Output. The internal reference connects to this pin. It may be scaled externally, and tied to the
REF_IN input to provide the converter’s reference voltage. Care must be taken in connecting external
circuitry to this pin. This pin is in a high impedance state during Sleep mode.
10
SDAT Digital Output (push-pull). This is the microPort™ serial data output. SDAT is driven low while the
TC3405 is converting data, effectively providing a “busy” signal. After the conversion is complete,
every high to low transition on the SCLK pin puts a bit from the resulting data word on the SDAT pin
(from MSB to LSB).
11
ENABLE Digital Input. When this input control is pulled low, the part is internally restarted. That is, any data
conversion or data read sequence is cleared and the part goes into Sleep mode. When ENABLE
returns high, the part resumes normal operation.
12
RESET Digital Output (open drain). This is the output of the V_DD monitor reset generator. RESET is driven low
when a Power-on Reset or Brown-out condition is detected.
See Section 1.0, AC Electrical Characteristics.
13
A1 Digital Input. Controls analog multiplexer in conjunction with A0 to select one of the four input
channels. This address is latched at the falling edge of the SCLK, which starts an A/D conversion.
A1, A0 = 00 = Input 1; 01 = Input 2; 10 = Input 3; 11 = Input 4.
14
A0 Digital Input. Controls analog multiplexer in conjunction with A1 to select one of the four input
channels. This address is latched at the falling edge of the SCLK, which starts an A/D conversion. A1,
A0 = 00 = Input 1; 01 = Input 2; 10 = Input 3; 11 = Input 4.
15
SCLK Digital Input. This is the microPort™ serial clock input. The TC3405 comes out of Sleep mode and a
conversion cycle begins when this pin is driven low. After the conversion starts, each additional
falling edge (up to six) detected on SCLK for t₄ seconds, reduces the A/D resolution by one bit. When
the conversion is complete, the data word can be shifted out on the SDAT pin by clocking the SCLK
pin.
16
V_DD Power Supply Input.
© 2002 Microchip Technology Inc.
DS21414B-page 5