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PDF DS2490 Data sheet ( Hoja de datos )
| Número de pieza | DS2490 | |
| Descripción | USB to 1-Wire Bridge Chip | |
| Fabricantes | Dallas Semiconducotr | |
| Logotipo |  |
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19-4993; 10/09
www.maxim-ic.com
FEATURES
Communicates at regular and overdrive 1-
Wire® speeds
Supports stiff 5V pullup for EEPROM,
sensors, and crypto iButton®
Slew rate controlled 1-Wire timing and active
pullup to accommodate long 1-Wire network
lines and reduce radiation
Programmable 1-Wire timing and driver
characteristics accommodate a wide range of
1-Wire network configurations
Low- to high-level command types, including
macros, for generating 1-Wire communication
Crystal oscillator timebase provides precision
timed 1-Wire waveforms
High-speed 12Mbps Universal Serial Bus
(USB) interface
Integrated USB-compliant transceiver
Supports USB remote wake-up from a 1-Wire
device event to resume a suspended host
system
0oC to +70oC operating temperature range
DS2490
USB to 1-Wire Bridge Chip
PIN ASSIGNMENT
PMOD
NC
NC
NC
VB
SUSO
D-
D+
NC
1-WIRE
NC
GND
1
2
3
4
5
6
7
8
9
10
11
12
24 VD
23 NC
22 NC
21 NC
20 XO
19 XI
18 NC
17 VD2
16 NC
15 NC
14 NC
13 NC
24-Pin SO
Top View
(300-mil)
ORDERING INFORMATION
PART NUMBER
TEMP
RANGE
PIN-PACKAGE
DS2490S+
0oC to +70oC 24 SO (300 mil)
DS2490S+T&R
0oC to +70oC 24 SO (300mil)
+ Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
DESCRIPTION
The DS2490 is a bridge chip that enables communication between a USB host system and a 1-Wire bus.
It provides regular, overdrive, and flexible 1-Wire communication speeds and a full-speed 12Mbps
connection to USB. USB vendor-specific commands defined in this specification are used to control the
DS2490 and communicate with attached 1-Wire devices. A functional block diagram of the DS2490 is
shown in Figure 1.
1-Wire and iButton are registered trademarks of Maxim Integrated Products, Inc.
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1 page  
ACTIVE PULLUP Figure 3
5V
VIAPTO
tAPUOT
DS2490
VIAPO
0V
1-Wire bus
is discharged
t1
t2 t3
The circuit operates as follows: At t1, the pulldown (induced by the DS2490 or a device on the bus) ends.
From this point on the 1-Wire bus is pulled high by the weak pullup current IWEAKPU provided by the
DS2490. The slope is determined by the load on the bus and the value of the pullup current. At t2, the
voltage crosses the threshold voltage VIAPO. Now, the DS2490 switches over from the weak pullup
current IWEAKPU to the higher current IACTPU. As a consequence, the voltage on the bus now rises faster.
As the voltage on the bus crosses the threshold VIAPTO at t3, a timer is started. As long as this timer is on
(tAPUOT), the IACTPU current will continue to flow. After the timer is expired, the DS2490 will switch back
to the weak pullup current.
Falling Edges (DS2490-initiated)
Whenever the DS2490 begins pulling the 1-Wire bus low to initiate a time slot, for example, it first turns
off the weak pullup current IWEAKPU. Then, at regular and overdrive speed it will generate a falling edge at
a slew rate of typically 15 V/µs. This value is acceptable for short 1-Wire busses and adequate for
communication at overdrive speed. For 1-Wire networks of more than roughly 30m length, flexible speed
should always be used. One of the parameters that is adjustable at flexible speed is the slew rate of
DS2490-initiated falling edges. The effect of the slew rate control is shown in Figure 4.
SLEW RATE CONTROL Figure 4
tF
Target for
long lines:
5V 4 ± 0.5 µs
low slew rate
high slew rate
0.8 V
0V
1-Wire bus
is pulled up
weak pull-up ends,
t 1 pull-down begins
Extensive tests have shown that 1-Wire networks with lengths of up to 300m will perform best if the fall
time tF is in the range of 4 ± 0.5µs. This translates into a slew rate of approximately 1V/µs. This slew rate
is typically achieved by selecting a PULLDOWN SLEW RATE parameter code of 0 x 4 (see MODE
COMMANDS). If the actual measured fall time is longer than the target value, a parameter code of 0 x 3
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5 Page 
DS2490
1-Wire Interface Alternate Setting Summary Table 2
Alt Setting
EP1
poll interval
EP2/EP3
max packet size
Alternate Setting Description
0
10ms
16 bytes
Long interrupt polling interval, small packet size for
bulk pipes
1
10ms
64 bytes
Long interrupt polling interval, large packet size for
bulk pipes
2
1ms
16 bytes
Short interrupt polling interval, small packet size
for bulk pipes
3
1ms
64 bytes
Short interrupt polling interval, large packet size for
bulk pipes
Endpoint Feature Summary Table 3
Endpoint Transaction
# Type
Direction1
0 CONTROL IN/OUT
1 INTERRUPT
IN
2 BULK
OUT
3 BULK
IN
1. Direction in this table is in reference to the Host
Max. Packet Size
ALT I/F-0..3: 8 bytes
ALT I/F-0..3 32 bytes
ALT I/F-0: 16 bytes
ALT I/F-1: 64 bytes
ALT I/F-2: 16 bytes
ALT I/F-3: 64 bytes
ALT I/F-0: 16 bytes
ALT I/F-1: 64 bytes
ALT I/F-2: 16 bytes
ALT I/F-3: 64 bytes
USB Core Commands Table 4
Standard Device Requests Target Element
SET_ADDRESS
Device
SET_CONFIGURATION Device
GET_CONFIGURATION Device
GET_DESCIPTOR
Device
GET_INTERFACE
Interface 0
SET_INTERFACE
Interface 0
SET_FEATURE
Device
CLEAR_FEATURE
Device
GET_STATUS
Device, Interfaces,
Endpoints 0-3
Range
0x01 - 0x1F
0x00 - 0x01
0x00 - 0x01
Interface 0: 0x00 - 0x03
Interface 0: 0x00 - 0x03
Notes
1
2
3
3
4
4
5, 6
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet DS2490.PDF ] | |
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