MIC2871 datasheet(13/24 Pages) MICREL

13 / 24 page

Micrel, Inc.

MIC2871

May 29, 2013

052913-1.0 (while in progress)

Revision 1.0 (final document)

Figure 3. Data Word Pulse Timing

A pulse is delimited by the signal first going below VL and

then above VH within the latch timeout TLAT. During this

transition, minimum on (TON) and off (TOFF) periods are

observed to improve tolerance to glitches.

Each rising

edge increments the internal data register.

Data is

automatically latched into internal shadow address and

data registers after an inactivity period of >TLAT.

To send register write commands, the address and data

are entered in series as two data words using the above

pattern, with the second word starting after the first latch

period has expired. After the second word is entered, the

IDLE command should be issued by leaving the DC pins

high for ≥ T

END.

After receiving the stop sequence, the internal registers

decode and update cycle is started, with the shadow

shows an example of entering a write of data 5 to

address 3.

Figure 4. Communication Timing Example of Entering Write

for Data 5 to Address 3

Only correctly formatted address/data combination will be

treated as a valid frame and processed by the MIC2871.

Any other input, such as a single data word followed by

TEND, or three successive data words will be discarded by

the target hardware as an erroneous entry. Additionally,

any register write to either an invalid register or with

invalid register data will also be discarded.

MIC2871 Registers

The MIC2871 supports five writeable registers for

controlling the torch and the flash modes of operation as

shown in Table 2. Note that register addressing starts at

1. Writing any value above the maximum value shown for

each registers will cause an invalid data error and the

frame will be discarded.

Table 2. Five Writable Registers of MIC2871

Address

Name

Max.

Value

Description

FEN/FCUR

Flash Enable/Current

TEN/TCUR

Torch Enable/Current

STDUR

Safety Timer Duration

LB_TH

Low Battery Voltage

Detection Threshold

ST_TH

Safety Timer Threshold

Flash Current Register (FEN/FCUR: default 0)

The flash current register enables and sets the flash

mode current level. Valid values are 0 to 31; values 0

−

15 will set the flash current without enabling the flash

(such that it can be triggered externally), values 16

− 31

will set the flash current and enable the flash. The flash

current register maps into the internal FEN and FCUR

registers as shown in the table below. Table 3 describes

the

relationship

between

the

flash

current

percentage of maximum current, and the FCUR register

setting.

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