LTM2893 datasheet(8/32 Pages) LINER

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LTM2893/LTM2893-1

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PIN FUNCTIONS

Logic Side

(All Inputs and Outputs Referenced to VL and GND)

ON (A1): Enable Input. A high input enables the logic side.

When ON is low and VL is high, MOSI, SCK, CNV, MISOA,

and MISOB are high impedance, an external pull-up or

pull-down resistor (100k or greater) is required on each

pin to minimize possible internal shoot though current if

these pins float.

SS (A2): Slave Select Input (Low True Slave Chip Select).

A low on the SS input enables MISOA and MISOB. To clear

faults or write the configuration register the SS input must

be high. With the LTM2893, the SS input may remain low

between ADC reads. With the LTM2893-1, the SS input

must frame the SCK transitions and not exceed the defined

watchdog timeouts. The SS pin contains a weak pull up

to the VL supply. CSC must be high for SS to be enabled.

MOSI (A3): Master Out Slave In Input. MOSI is the serial

data input for the configuration registers or input for se-

rial data to be written to the isolated ADC through MOSI2,

(LTM2893-1option).WhenMOSIisnotused,MOSIshould

be connected to GND. Connect a weak pull-up to VL or

a weak pull-down to GND to maintain a valid logic input

when MOSI is not driven.

SCK (A4): Serial Port Clock Input. MISOA and MISOB data

change after a rising edge of the SCK input. MOSI data

is read in on the rising edge of the SCK input. Connect a

weak pull-up to VLoraweakpull-downtoGNDtomaintain

a valid logic input when SCK is not driven.

BUSY (A5): Busy Output. A high output indicates the ADC

is currently converting a result. On the falling edge of the

BUSY output the data is ready to be read out of the serial

digital interface. At startup, a high on the BUSY output

indicates the isolated side is not ready. Once the BUSY

output goes low the system is ready.

CNV (A6): Conversion Start Input. The rising edge of CNV

is transferred to CNV2 with minimal delay and minimal

jitter. Do not change the CNV input during a read of the

serial digital interface. The falling edge of CNV is ignored.

VL (B1): Interface Logic Supply. Recommended operating

voltage is 1.71V to 5.5V. Interface supply voltage for pins

SA, SB, SC, MISOA, MISOB, MOSI, SCLK, SS, CSC, BUSY,

and CNV. Internally bypassed to GND with 1µF.

MISOA (B2): Master In Slave Out A Output. Serial data

output containing the ADC result from MISOA2. Connect a

weak pull-up to VLoraweakpull-downtoGNDtomaintain

a valid logic level when MISOA is high impedance while

SS is high.

MISOB (B3): Master In Slave Out B Output. Serial data

output containing the ADC results from MISOB2. Con-

nect a weak pull-up to VL or a weak pull-down to GND to

maintain a valid logic level when MISOB is high impedance

while SS is high..

CSC (B4): Chip Select Configuration Input (CSC Chip

Select). A low on the CSC input enables access to the

configuration register. The Configuration Register section

describes configurable options. SS must be high for CSC

to be enabled.

GND (B5): Connect to GND.

FAULT (B6): Fault Output Open Drain. A low on the FAULT

output indicates a communication or command error.

Connect to an external 4.7k pull-up to VL to monitor fault

events.

VCC (C1): Supply Voltage. Recommended operating volt-

age is 3.0V to 5.5V. Internally bypassed to GND with 1µF.

GND (C2-C3): Circuit Ground. Return for VL logic supply

and VCC supply.

SA (C4): Select Enable Input A. Select signal pass through

to SA2 to control an external multiplexer or programmable

gain amplifier. Transitions must not occur just before the

beginning of a CNV or SS edge. See the Safe Regions of

the Select Enable Signals section for timing constraints.

Do not use as a general purpose asynchronous signal. SA

containsaweakpulldown.ConnecttoGNDwhennotused.

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