MAX1441GUP/V+ Maxim Integrated Products, MAX1441GUP/V+ Datasheet - Page 10

• Manufacturer Part Number: MAX1441GUP/V+
• Description: Touch Screen Converters & Controllers PROXIMITY SENSR el Proximity and Tou
• Manufacturer: Maxim Integrated Products

Specifications of MAX1441GUP/V+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 1. Important AFE Function Registers
Automotive, Two-Channel Proximity and
Touch Sensor
To avoid interference, the excitation frequency can be
adjusted to automatically spread within a frequency
range. The lower frequency bound and spread-spectrum
bandwidth registers determine this range. Spread spec-
trum continuously changes the excitation frequency so
that the radiated power is distributed over a frequency
range rather than a single frequency. This lowers the
radiated energy density and thus leads to a cleaner
spectrum. In addition, by changing the excitation fre-
quency, the capacitance measurement becomes more
immune against interference signals.
In case the capacitance measurement permanently
reaches the upper or lower limit, there is a likelihood of
a parasitic capacitance on top of the touch pads. This
could be an ice coating on the door handle for example.
In this case, the offset capacitance is adjusted so that
the capacitance reenters the measurement range. A
parasitic capacitance up to 63pF is compensated for
each channel independently by properly setting the off-
set registers, CO1/CO2.
10
CRNG
FEL
FEB
CO1, CO2
SCT
DSB
SSB2
PD
WU1, WU2
AT1H, AT2H
RT1H, RT2H
CRSLT1L, CRSLT1H
CRSLT2L, CRSLT2H
AFEINTST
REGISTER
Adjust the capacitance range
Set the frequency of excitation
Set the bandwidth of the spread-
spectrum modulation
Set the capacitance offset
Put the device in single-conversion
mode
Set the standby conversion rate
Set the channel 2 standby conver-
sion rate subdivider
Put the AFE in power-down mode
(does not affect CPU operation)
Select the wakeup criteria (rate-of-
change and/or absolute capacitive
change)
Set the absolute wake-up thresh-
old
Set the capacitance rate-of-
change threshold
Channel 1 conversion result
Channel 2 conversion result
Interrupt status of the AFE
Excitation Frequency
Offset Capacitance
FUNCTION
The C2D converter can be placed into a single conver-
sion mode. In the single conversion mode, the micro-
controller triggers a single conversion by setting bit SCT.
If the single conversion mode is enabled, the analog
front-end powers up only during the conversion. SCEN
controls the single conversion mode. SCEN = 1 enables
the single conversion mode and SCEN = 0 disables the
single conversion mode. When single conversion mode
is enabled, set bit SCT to trigger a conversion. SCT bit
automatically clears after the conversion is completed.
To save power, the analog front-end can be put in the
standby state. During standby, the conversion rate is
determined by the standby state conversion rate divider.
SB controls the standby mode. SB = 1 enables the stand-
by mode and SB = 0 disables the standby mode. There is
only 1 SB bit common to both channels, so the channels
cannot be placed in the standby state independently.
The following sequence of control register writes to the
PD register is recommended for entering standby mode:
1) Set PD to 06h to put both AFE channels into reset state.
2) Write DSB and SSB2 registers to set standby rate (if
3) Set PD to 00h to release AFE reset.
4) Set PD to 01h to enter standby mode.
The maximum C2D conversion rate is 1.66kHz. Standby
state uses conversion-rate reduction to save power. The
conversion rate divider and conversion rate subdivider
determine the final conversion rate. The DSB divider
DSB[4:0] is common to both sensor channels. The con-
version rate for channel 2 can be further reduced by the
SSB2[4:0] divider. The conversion rate in kHz is deter-
mined by the equation:
where D is an integer number determined by a 5-bit word
DSB[4:0] and S is an integer number determined by a
5-bit word SSB2[4:0]. The default value of D and S is
one. D > 1 when S > 1.
not already set).
Standby State Conversion-Rate Divider
f
conv,channel2
f
conv,channel 1
Single Conversion Mode
=
=
D S
D
1
1
×
×
1.66kHz
×
1.66kHz
Standby Control