Figure 37:
OTP Register Analog Read
AS5040 − Programming the AS5040
This current must be provided by an external voltage source. If
this voltage source cannot provide adequate power, the zener
diodes may not be programmed properly.
In order to verify the quality of the programmed bits, an analog
level can be read for each zener diode, giving an indication
whether this particular bit was properly programmed or not.
To put the AS5040 in analog readback mode, a digital sequence
must be applied to pins CSn, Prog and CLK as shown in
Figure 37. The digital level for this pin depends on the supply
configuration (3.3V or 5V; see 3.3V / 5V Operation).
The second rising edge on CSn (OutpEN) changes pin Prog to a
digital output and the log. high signal at pin Prog must be
removed to avoid collision of outputs (grey area in Figure 37).
The following falling slope of CSn changes pin Prog to an analog
output, providing a reference voltage Vref, that must be saved
as a reference for the calculation of the subsequent
programmed and unprogrammed OTP bits. Following this step,
each rising slope of CLK outputs one bit of data in the reverse
order as during programming (see Figure 37):
Md0-MD1-Div0,Div1-Indx-Z0…Z9, ccw)
During analog readback, the capacitor at pin Prog (see
Figure 35) should be removed to allow a fast readout rate. If the
capacitor is not removed the analog voltage will take longer to
stabilize due to the additional capacitance.
The measured analog voltage for each bit must be subtracted
from the previously measured Vref, and the resulting value gives
an indication on the quality of the programmed bit: a reading
of <100mV indicates a properly programmed bit and a reading
of >1V indicates a properly unprogrammed bit.
A reading between 100mV and 1V indicates a faulty bit, which
may result in an undefined digital value, when the OTP is read
at power-up.
Following the 16th clock (after reading bit “ccw”), the chip
must be reset by disconnecting the power supply.
ProgEN
CSn
Prog
CLK
O u tpE N
Analog Readback Data at Prog
P ow e r-o n-
R e s e t;
turn off
s u p p ly
V ref
V program m ed
Internal
test bit
digital
M d0 M d1 D iv0 D iv1 V unprogrammed Z5 Z6 Z7 Z8 Z9 ccw
Prog changes to O utput
1
16
tL o a d P ro g
C LK Aread
Page 36
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ams Datasheet
[v2-12] 2017-Jun-20