TSA7887BRZ datasheet(10/20 Pages) TOUCHSTONE

部件名	TSA7887BRZ

功能描述	A Micropower, 2-channel, 125-ksps, Serial-Output 12-bit SAR ADC

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制造商	TOUCHSTONE [Touchstone Semiconductor Inc]

网页	http://www.touchstonesemi.com

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TSA7887

Page 10

TSA7887DS r1p0

RTFDS

Typical Application Circuit

Figure 4 shows a typical application circuit for the

TSA7887 where the

ADC’s GND pin is connected to

the analog ground plane of the system. In this

application

circuit,

the

TSA7887

has

been

configured for two-channel operation so

the ADC’s

VREF is internally connected to VDD; as a result,

the analog input range on either analog input is 0V

to VDD. It is always considered good engineering

practice to b

ypass the ADC’s VDD with good quality

capacitors

with

short

leads

(surface-mount

components are preferred) and located a very short

distance from the ADC. The conversion result at the

DOUT pin is a 16-bit word with four leading zeros

followed by the MSB of the 12-bit conversion result.

In low-power applications, automatic-power-down-at-

the-end-of-conversion modes (PM Modes 3 or 4)

should be used to improve

the ADC’s power

consumption-versus-throughput rate performance.

For additional information on the TSA7887’s four

power

management

operating

modes,

please

consult

the

Operating

Modes

section

of

the

datasheet.

Analog Input Details

An equivalent circuit of the analog input structure of

the TSA7887 is illustrated in Figure 5 where diodes

D1 and D2 serve as ESD-clamp protection for the

analog inputs. Since there are diodes from the

analog input to both VDD and GND, it is important

any forward conduction of current in D1 or D2 is

avoided. Thus, the analog input signal should never

exceed the either VDD or GND by more than

200mV. Even though the maximum current these

diodes can conduct without causing irreversible

damage to the ADC is 20mA, any small amount of

forward diode current into the substrate because of

an overvoltage condition on an unselected channel

can cause inaccurate conversion results on the

selected channel.

Attributed to parasitic package pin capacitance,

capacitor C1 in Figure 5 is typically about 1 pF.

Resistor R1 is the equivalent series resistance of the

TSA7887’s input multiplexer and input sampling

switch and is approximately 100

Ω. Capacitor C2 is

the ADC sampling capacitor and has a typical

capacitance of 10 pF.

In signal-acquisition (or ac) applications, the use of

an external R-C low-pass filter on either or both

analog inputs can be useful in removing out-of-band

high-frequency components from the analog input

signal. In applications where harmonic distortion and

signal-to-noise ratio performance are important, the

analog input(s) should be driven from a low-

impedance source. Large source impedances will

affect significantly the

TSA7887’s ac performance.

To lower the driving-point impedance level may

impose the use of an input buffer amplifier. The

optimal choice for the external drive op amp will be

determined by application requirements as well as

the TSA7887’s dynamic performance.

When the analog input is not driven by an external

amplifier, the driving-point source impedance should

be low. The maximum source impedance will

depend upon the amount of total harmonic distortion

(THD) that can be tolerated in the application. THD

will increase as the source impedance increases

Figure 4: TSA7887's Typical Application Circuit.

Figure 5:

TSA7887’s Analog Input Equivalent Circuit.

INPUT FREQUENCY - kHz

VDD = 5V

5V External Reference

-65

-75

-85

-90

0.2

10

30

50

20

-60

Figure 6: TSA7887 THD vs Analog Input Frequency

RIN = 50

Ω, CIN = 2.2nF

RIN = 10

Ω, CIN = 10nF

-70

-80

40

类似零件编号 - TSA7887BRZ

制造商	部件名	数据表	功能描述
Silicon Laboratories	TSA7887BRZ	1Mb / 21P	A Micropower, 2-channel, 125-ksps, Serial-Output 12-bit SAR ADC
Silicon Laboratories	TSA7887BRZ-REEL	1Mb / 21P	A Micropower, 2-channel, 125-ksps, Serial-Output 12-bit SAR ADC

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类似说明 - TSA7887BRZ

制造商	部件名	数据表	功能描述
Silicon Laboratories	TSA7887	1Mb / 21P	A Micropower, 2-channel, 125-ksps, Serial-Output 12-bit SAR ADC
Touchstone Semiconducto...	TS7001	1Mb / 20P	A Micropower, 2-channel, 187.5-ksps, Serial-Output 12-bit SAR ADC
Silicon Laboratories	TS7001	1Mb / 21P	A Micropower, 2-channel, 187.5-ksps, Serial-Output 12-bit SAR ADC
Analog Devices	AD7887	465Kb / 25P	Micropower, 2-Channel, 125 kSPS, 12-Bit ADC in 8-Lead MSOP
	AD7888	245Kb / 18P	Micropower, 8-Channel, 125 kSPS, 12-Bit ADC in 16-Lead TSSOP
	AD7866ARUZ	585Kb / 24P	Dual 1 MSPS, 12-Bit, 2-Channel SAR ADC with Serial Interface REV. A
	AD7866	304Kb / 20P	Dual 1 MSPS, 12-Bit, 2-Channel SAR ADC with Serial Interface REV. 0
	AD7866	585Kb / 24P	Dual 1 MSPS, 12-Bit, 2-Channel SAR ADC with Serial Interface REV. A
	AD7866	430Kb / 25P	Dual 1 MSPS, 12-Bit, 2-Channel SAR ADC with Serial Interface
	AD7887	133Kb / 16P	2.7 V to 5.25 V, Micropower, 2-Channel, 125 kSPS, 12-Bit ADC in 8-Lead uSOIC REV. B