MMBTA92LT1 Просмотр технического описания (PDF) - Silicon Laboratories

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MMBTA92LT1

Global ISOmodem-EVB

Silicon Laboratories 

Si2493/57/34/15/04

Global ISOmodem-EVB

card and the RJ-11 phone jack.

2.1.1. Voltage Regulator/Power Supply

The input voltage to either J8 or J9 must be between 7.5

and 13.5 V dc or 7.5 and 13.5 VPEAK ac. The

motherboard includes a diode bridge (D12) to guard

against a polarity reversal of the dc voltage or to rectify

an ac voltage. The power source must be capable of

continuously supplying at least 100 mA. C44 serves as

a filter cap for an ac input. The voltage regulator, U10,

provides 5 V for the motherboard and the input for

voltage regulator U3, which outputs 3.3 V for use on the

motherboard and to power the daughter card. Si24xxDC

power consumption can be measured by placing a

meter across R59. Power is supplied to U2 through D5

from the USB.

2.1.2. Reset Circuitry

The Si2493/57/34/15/04 requires a reset pulse to

remain low for at least 5.0 ms after the power supply

has stabilized during the powerup sequence or for at

least 5.0 ms during a power-on reset. Most production

Si2493/57/34/15/04 modem chipset applications require

that RESET be controlled by the host processor. Certain

Si2493/57/34/15/04 operation modes, including

powerdown, require a hardware reset to recover.

The Si2493/57/34/15/04-EVB contains two reset

options, an automatic power-on reset device, U18

(DS1818) (default), and a manual reset switch (S1) to

permit resetting the chip without removing power. A

reset, regardless of the mechanism, causes all modem

settings to revert to factory default values.

2.1.3. Automatic Reset (DS1818)

The DS1818 is a small, low-cost device that monitors

the voltage on VD and an external reset pushbutton. If

VD drops below 3.0 V, the DS1818 provides a 220 ms

active-low reset pulse. On powerup, the DS1818 also

outputs an active low reset pulse for 220 ms after VD

reaches 90% of the nominal 3.3 V value. The DS1818

outputs a 220 ms reset pulse any time the power supply

voltage exceeds the 3.3 V ±10% window.

2.1.4. Manual Reset

The manual reset switch (S1) performs a power-on

reset. This resets the Si2493/57/34/15/04 to factory

defaults without turning off power. Pressing S1 activates

the reset monitor in the DS1818 and produces a 220 ms

active low reset pulse.

2.1.5. EEPROM Enable (FT Only)

Connecting JP34 and JP35 enables the optional

EEPROM, U5. See “AN93: Si2457/Si2434/Si2415/

Si2404 Modem Designer’s Guide” for programming

details.

2.1.6. Interface Selection

The serial interface of the Si2493/57/34/15/04-EVB can

be connected to a computer, terminal, embedded

system, or any other data terminal equipment (DTE) via

a standard RS-232 interface, USB interface, or through

a direct TTL serial interface.

The Si2493/57/34/15/04 can be tested as a standard

data modem by connecting the Si2493/57/34/15/04-

EVB to a personal computer or other DTE power supply

and a phone line. A PC can communicate with the

Si2493/57/34/15/04-EVB using a standard terminal

program, such as HyperTerm or ProComm.

Jumper settings determine how the Si2493/57/34/15/

04-EVB is connected to the DTE.

2.1.7. RS-232 Interface

This operation mode uses the standard factory jumper

settings illustrated in Figure 1 on page 3. The Maxim

MAX3237 transceiver interfaces directly with the TTL

levels available at the serial interface of the Si2493/57/

34/15/04 and, using internal charge pumps, makes

these signals compatible with the RS-232 standard. The

RS-232 transceiver on the Si2493/57/34/15/04-EVB can

communicate at rates between 300 bps and 1 Mbps.

This simplifies the connection to PCs and other data

terminal equipment (DTE). The signals available on the

Si2493/57/34/15/04-EVB serial interface (DB9

connector) are listed in Table 3.

2.1.8. USB Interface

The USB cable connects to J10 on the motherboard

and provides both data and power. Installing a jumper

on JP23 enables the USB interface and disables the

RS-232 interface. The USB interface is provided by

U12. A USB driver for this chip is available for most PC

and MAC operating systems on the CD.

Rev. 0.7

9

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