ISL73148SEHFSLASHPROTO datasheet(52/59 Pages) RENESAS

52 / 59 page

R34DS0023EU0103 Rev.1.03

Page 52

Feb 23, 2023

ISL73148SEH Datasheet

specifications, the settling time must be met for the input signals on the analog input of the ISL73148SEH. To

accurately resolve to 1 LSB, the settling time is defined by Equation 4:

Simplifying this results in Equation 5:

Solving for t results in:

, which can be written as

and further simplified to

Settling time is t, RS ×CP is τ, and the resolution of the ADC is N.

The ISL73148SEH is a 14-bit ADC, which means the settling time to attain 1 LSB accuracy is 9.7 × τ. For

example, the ISL73148SEHEV1Z evaluation board employs a 24Ω resistor for RS and a 47pF capacitor for CP,

which means that the required settling time would be t = 0.693 × 14 × 24Ω × 47pF = 10.94ns. If different RS and

CP values are used, calculate the settling time for those conditions. These calculations assume the settling time of

the input network RS and CP are much larger than the settling time of any amplifier driving the ISL73148SEH

analog input. If this is not the case, the settling time of the input network must be root-sum-squared with the

settling time of the amplifier to determine the required settling time using Equation 6:

5.15 Static Power Dissipation

The ISL73148SEH can be placed into an operating mode where the device is ready to initiate a sample, but where

the power consumption is considerably reduced. While operating in normal mode, this low static power state can

be entered on initial power up by holding CS low or by holding CS low and asserting/de-asserting the PD pin.

While operating in low power mode, the ISL73148SEH must be powered up and have at least one sample

acquisition in with the LPM pin asserted to place the device into low power mode. Subsequently, the

ISL73148SEH can enter a low static power state by holding CS low and asserting/de-asserting the PD pin.

5.16 Cold Sparing Operation

The ISL73148SEH can be used in applications that require connections to multiple input devices with only one

active at a given time, which is commonly referred to as cold sparing. The analog input of the ISL73148SEH

connects to an 8-channel multiplexer with high impedance inputs. Only one channel can be selected at a given

time for sampling. In many cold-sparing applications, the unused devices connected to the unused channels are

completely powered down with the supply voltage removed. However, for the ISL73148SEH any device

connected to any one of the eight analog inputs should be provided a supply voltage, but may be placed into

power-down mode using the PD pin of the individual device.

(EQ. 4)

(EQ. 5)

(EQ. 6)

-------

–









–

















0.693 N





ttAMP



tRC



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