5

SP8537DS/03

SP8537 Micropower Sampling 10–Bit Voltage A/D Converter

© Copyright 2000 Sipex Corporation

The device uses a capacitive DAC architecture

which provides the sampling behavior. This

results in full Nyquist performance at the fastest

throughput rate (29.5 KHz) the device is capable of.

The power supply voltage is variable from 3.0V

to 5.5V which provides supply flexibility. At the

5.0V supply level, conversion plus sampling

time is 33.9

µS and supply current is 250µA

(1.25 mW). With a 3.3V supply the conversion

plus sampling time is 150.2

µS and current is

reduced to 150

µA (0.5 mW).

The device features automatic shutdown and

will shutdown to a +0.5

µA power level as CS

is brought high (de-selected). Power is

proportional to conversion duty cycle and

varies from 250

µA at 34µS (Duty cycle =

100%) to 6.25

µa at 1.4 ms (Duty cycle = 2.5%).

Examples:

Conversion rate

I

Duty Cycle

34

µS

250

µA

100%

68

µS

125

µA

50%

136

µS

62.5

µA

25%

1.4 mS

6.25

µA

2.5%

DESCRIPTION

The SP8537 is a 10 bit sampling ADC with

a programmable two channel multiplexer and

serial data interface. The ADC samples and

converts 10 bits of data in 33.9

µS with a 5V

supply voltage applied. The SP8537 will also

operate at a 3.3V supply at 150.2

µS throughput.

The device automatically shuts down to a

+0.5

µA (MAX) level as soon as the chip is

deselected (CS=1). Serial data output is

available in an MSB first format.

FEATURES

Two program bits, which are shifted into the

device prior to conversion, determine the input

configuration. In the single ended MUX

configuration the input signal will be applied to

either channel 0 or channel 1 and will be ground

referenced. The maximum full scale range is

VCC. In the full differential mode, the signal

will be applied between channel 0 and channel

1. The signals applied at each input may both

be dynamic. This is in contrast with pseudo

differential devices which must have input low

held at a constant level during conversion. The

converter will provide significant common mode

rejection when used in full differential manner.

Both inputs must remain between ground and

VCC for proper conversion.

MUX ADDRESSING

Mux Addressing

Channel #

GND

Comments

SGL/DIFF

ODD/SIGN

0

1

0

0

V

INH

V

INL

Full Differential Mode

0

1

V

INL

V

INH

1

0

V

INH

Single Ended Mux Mode

1

1

V

INH

INPUT VOLTAGE

INPUT VOLTAGE

OUTPUT

(V

AT V

CODE

0 LSB

0V

0000000000

1 LSB

0.0049V

0000000001

512 LSB

2.5000V

1000000000

1022 LSB

4.9902V

1111111110

1023 LSB

4.9951V

1111111111

* See Mux Addressing Table for a definition of V

ADC TRANSFER FUNCTION

V

INL

V

INL