EVM692AHJ データシートの表示（PDF） - Semtech Corporation

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EVM692AHJ

200 MHz Monolithic Dual Pin Electronics Driver

Semtech Corporation 

EDGE HIGH-PERFORMANCE PRODUCTS

Circuit Description (continued)

The desired value for the external resistor can be

determined from the relationship:

IBIAS = (VCC - .7) / (Rext + 50).

The actual IBIAS level is determined by selecting the

desired performance and power level. The charts listed

in the Application Information section enable the user

to quickly determine the appropriate bias level.

Thermal Monitor

The Edge692 includes an on-chip thermal monitor

accessible through the THERMAL DIODE pin. This node

connects to 5 diodes in series to VEE (see Figure 2) and

may be used to accurately measure the junction

temperature at any time.

Slew Rate Adjustment

The driver rising and falling slew rates are adjustable

from 2 V/ns to 1 V/ns. The actual slew rate realized is a

function of the chip bias and slew rate adjust input

currents.

The SLEWADJ input is determined by selecting the

desired performance and power level (after the BIAS

current is first chosen.) The charts listed in the

Application Information section enable the user to quickly

determine the appropriate SLEWADJ level.

SLEWADJ is a current controlled input that varies the

rising and falling edge slew rates. Ideally, a current DAC

would be used to establish this current. However, a

resistor to a positive voltage, typically VCC, is acceptable.

Thermal Diode

Bias Current

Figure 3 shows a simplified schematic of the SLEWADJ

input stage. Once a desired input current is selected,

the external resistor value is determined by the following

relationship:

˚ Temperature coefficient = –10 mV/ C

(VCC - .7) / (Rext + 860) = Islewadj.

VCC

SLEWADJ

REXT

VEE

Figure 2. Thermal Diode String

1.72K

1.72K

A bias current of 100 µA is injected into this node, and

the measured voltage corresponds to a specific junction

temperature with the following equation:

TJ(˚C) = {[(VTHERMAL DIODE – VEE) / 5] – .7} / (–.00208).

Iradj

Ifadj

Figure 3. SLEWADJ input circuitry

Notice that the driver A slew rate and driver B slew rate

are independent. However, the rising and falling edge

slew rates on each driver track each other and are not

independent.

 2000 Semtech Corp.

5

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