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PDF MAX1441 Data sheet ( Hoja de datos )
| Número de pieza | MAX1441 | |
| Descripción | Two-Channel Proximity and Touch Sensor | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-5310; Rev 0; 7/10
EVAALVUAAILTAIOBNLEKIT
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Automotive, Two-Channel Proximity and
Touch Sensor
General Description
The MAX1441 proximity and touch sensor IC is designed
for capacitive proximity sensing in automotive passive
remote keyless entry (PRKE) and other applications.
This device provides signal processing to support
two independent touch/proximity sensor channels. The
device features two open-drain output pins with high-
voltage capability up to 28V, as well as five digital I/Os
to indicate sensing events. During manufacturing, JTAG
programming uses four digital I/Os.
The device uses grounded electrode capacitive sens-
ing to measure capacitance between one of the two
sense pins and the ground. A hand approaching a
sense electrode attached to these sense pins causes
a change in measured capacitance indicating the
presence (touch or proximity) of the object. Active-
guard outputs shield the sense electrode from unwant-
ed sources without adding parasitic capacitance.
Spread-spectrum techniques in the sensor excitation
circuit reduce both electromagnetic emissions and
susceptibility to interfering signals. In addition, the
sensing excitation frequency is programmable from
100kHz to 500kHz in 10kHz steps to avoid interference.
The sensor input signals are converted to a 12-bit
digital data and are available to an on-chip microcon-
troller (FC). The device provides independent offset
compensation of up to 63pF for each input channel.
Each channel can be programmed to 5pF, 10pF, or 20pF
full-scale range.
The device features an internal MAXQ® microcontroller
with 2kword of flash for user programs and 128 bytes
of SRAM. This feature provides the ability to implement
customized signal processing and discrimination
algorithms that optimize performance in the systems.
The device offers user-configurable general-purpose
digital I/O lines. Power-on-reset (POR) circuitry provides
consistent startup of the device, and a watchdog
timer ensures long-term reliable operation of the user’s
software.
The device is available in a 20-pin TSSOP package and
is specified over the -40NC to +105NC automotive tem-
perature range.
Features
S Low Average Operating Current (100µA at 14V)
S 1.2.fF LSB Capacitance-to-Digital Resolution (5pF
Range)
S 5V to 28V Operation
S 45V Overvoltage Protection
S Sinusoidal Excitation for Reduced EMI Emissions
S Frequency Spreading Operation for Reduced EMI
Susceptibility and Emissions
S Active-Guard-Sense Architecture Provides
Increased Flexibility in System Packaging
S CMOS/LVCMOS-Compatible Outputs
S Embedded µC Supports User-Specified Adaptive
Sense Algorithms
S 2kwords Flash Memory
S 128-Byte SRAM
S ±2kV ESD Immunity on Sensor I/O Lines
S JTAG Serial Interface
S Supports Two Independent Grounded Capacitor
Sensor Inputs
S -12V Reverse Voltage Protection with External
Diode
Applications
PRKE System Proximity Sensing
Object Detection Systems
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX1441GUP/V+ -40NC to +105NC
20 TSSOP
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V Denotes an automotive qualified part.
MAXQ is a registered trademark of Maxim Integrated
Products, Inc.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
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Automotive, Two-Channel Proximity and
Touch Sensor
Typical Operating Characteristics (continued)
(VBATT = 14V, VAA = VDD = 3.4V, TA = +25NC, unless otherwise noted.)
CAPACITANCE ERROR
vs. INTERFERENCE FREQUENCY OFFSET
60
10pF RANGE,
50 CO_ = 8,
300kHz
40 EXCITATION
FREQUENCY,
30 500mVP-P
INTERFERENCE
20 FREQUENCY
10
0
-10
100 150 200 250 300 350 400 450 500
INTERFERENCE FREQUENCY OFFSET (kHz)
CAPACITANCE ERROR
vs. EXCITATION BANDWIDTH
(WITH IN-BAND INTERFERENCE)
60
50
10pF RANGE,
CO_ = 8,
300kHz EXCITATION FREQUENCY,
40 300kHz, 500mVP-P
INTERFERENCE FREQUENCY
30
20
10
0
-10
0
50 100 150
EXCITATION BANDWIDTH (kHz)
200
OUTPUT POWER
vs. EXCITATION FREQUENCY SPECTRUM
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
0
200 400 600 800 1000
EXCITATION FREQUENCY SPECTRUM (kHz)
CAPACITANCE ERROR
vs. EXCITATION BANDWIDTH
0.5
0.4
5pF RANGE,
CO_ = 0,
0.3 3.6pF INPUT CAPACITANCE
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-10
10 30 50 70 90 110 130 150
EXCITATION BANDWIDTH (kHz)
100
90
80
70
60
50
40
30
20
10
0
0
DETECTION DISTANCE
vs. ATxH REGISTER SETTING
25cm x 2cm TOUCH PAD
5pF RANGE
20pF RANGE
10pF RANGE
5 10 15 20 25 30 35
ATxH REGISTER SETTING
FULL-SCALE CAPACITANCE CHANGE
vs. TEMPERATURE
3.0
2.5
20pF RANGE
2.0
1.5
10pF RANGE
1.0
0.5 5pF RANGE
0
-0.5
-1.0
-1.5
-50 -25
0 25 50 75 100 125
TEMPERATURE (°C)
5
5 Page 
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Automotive, Two-Channel Proximity and
Touch Sensor
Power-Down Control
Each sensor channel independently powers down
through the PD register. Bit value 1 powers down the
channel and bit value 0 powers up the channel. The
excitation source circuitry powers down if both chan-
nels are powered down. Powering down both channels
also resets all AFE internal circuits except for the AFE’s
control registers.
Wake-Up Event Thresholds
The sensor wakes up when the measured capacitance
exceeds a set capacitance threshold and/or a pre-
defined rate of change in the capacitance. When an
object approaches the sensor, the sensed capacitance
starts changing. Once the capacitance value crosses
the absolute value threshold and/or the capacitance
rate of change crosses the rate-of-change threshold, the
analog front-end is automatically put in the wake-up state
and the SB bit is cleared. At the same time, the wake-up
interrupt is sent to the microcontroller. The 8-bit word
ATx[11:4] determines the absolute wake-up threshold
and 8-bit word RTx[11:4] determines the rate-of-change
threshold. Only the upper 8 bits are used in the thresh-
old comparisons. Bit AOx determines if logical AND
or OR operation is performed on the absolute and the
rate-of-change threshold crossing events to produce the
wake-up event. Bit value 1 sets the AND operation and
bit value 0 sets OR operation. Both absolute and rate-
of-change threshold crossing detection can be enabled
or disabled using bits AEx and REx. AEx bit value 1
enables absolute value detection and REx bit value 1
enables rate-of-change detection. The thresholds can be
independently programmed in channels 1 and 2.
Conversion Result Word
The 12-bit result of the C2D conversion is available in
CRSLT1L and CRSLT1H for channel 1 and in CRSLT2L
and CRSLT2H for channel 2. Bit OVRx is set to 1 if the cur-
rent conversion caused overranging in the C2D converter.
Data Ready in Channel 1
The interrupt status bit IDR1 is set to 1 when a new
conversion result is available in channel 1. If the micro-
controller does not read the conversion result before the
next conversion is completed, the old conversion result
is overwritten.
Data Ready in Channel 2
The interrupt status bit IDR2 is set to 1 when a the new
conversion result is available in channel 2. If the micro-
controller does not read the conversion result before the
next conversion is completed, the old conversion result
is overwritten.
Wake-Up Event in Channel 1
The interrupt status bit IWUP1 is set to 1 when channel 1
detects a wake-up condition.
Wake-Up Event in Channel 2
The interrupt status bit IWUP2 is set to 1 when channel 2
detects a wake-up condition.
Detailed Controller Specification
Architecture
The device is based on the MAXQ RISC processor with
Harvard memory architecture.
Specific MAXQ Special-Purpose
Register Implementation
The device implements all other standard MAXQ special-
purpose registers (SPRs). For details, see the SPR bit
description in Table 5.
Special-Purpose Registers
Table 2 summarizes the SPRs and their address indexes.
These registers can be accessed by user software.
Table 2. Special-Purpose Register Map
MODULE
INDEX OF SPECIAL-PURPOSE REGISTER
MODULE SPECIFIER 00000 00001 00010 00011 00100 00101 00110 00111 01000 01001 01010 01011
AP
01000
AP APC —
— PSF IC IMR —
SC
—
—
IIR
A
01001
A0 A1 A2 A3
—
—
—
—
—
—
—
—
PFX 01011 PFX — — — — — — — — — — —
IP 01100 IP — — — — — — — — — — —
SP 01101 — SP IV — — — LC0 LC1 — — — —
DPC
01110
——
— Offs DPC GR GRL BP GRS GRH GRXL FP
DP
01111
——
— DP0 —
—
— DP1 —
—
—
CP
01100
—
—
—
—
—
—
—
01101
—
—
—
—
—
—
—
01110
CKCN
—
—
—
—
—
—
01111
WDCN
—
—
—
—
—
—
11
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| Páginas | Total 41 Páginas | |
| PDF Descargar | [ Datasheet MAX1441.PDF ] | |
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