ISL6740A

8

FN9195.3

February 9, 2012

Pin Descriptions

sum of the quiescent current and the average output current.

Knowing the operating frequency, Fsw, and the output loading

capacitance charge, Q, per output, the average output current

can be calculated from:

SYNC - A bidirectional synchronization signal used to

coordinate the switching frequency of multiple units.

Synchronization may be achieved by connecting the SYNC

signal of each unit together or by using an external master

required regardless of the synchronization method used. The

paralleled unit with the highest oscillator frequency assumes

control. Self-synchronization is not recommended for oscillator

frequencies above 900kHz. For higher switching frequencies,

an external clock with a pulse width less than one-half of the

oscillator period must be used.

control pin. A resistor is connected between this pin and GND.

The current flowing through the resistor determines the

magnitude of the charge current. The charge current is

nominally twice this current. The PWM maximum ON time is

determined by the timing capacitor charge duration. The

voltage appearing on this pin is nominally 80% of the voltage

applied to the UV/FF pin.

control pin. A resistor is connected between this pin and GND.

The current flowing through the resistor determines the

magnitude of the discharge current. The discharge current is

nominally 50x this current. The PWM deadtime is determined

by the timing capacitor discharge duration. The voltage

appearing on this pin is nominally 80% of the voltage applied

to the UV/FF pin.

pin and GND.

Typical Performance Curves

FIGURE 1. REFERENCE VOLTAGE vs TEMPERATURE

FIGURE 2. OSCILLATOR CT DISCHARGE CURRENT GAIN

FIGURE 3. DEADTIME (DT) vs CAPACITANCE

FIGURE 4. CAPACITANCE vs FREQUENCY

1.001

1

0.999

0.998

0.997

-40

-25

-10

5

20

35

50

65

80

95

110

TEMPERATURE (°C)

65

60

55

50

45

40

0

50

100

150

200

250

300

350

400

450

500

RTD CURRENT (µA)

100

10

10

20

30

40

50

60

70

80

90

100

RTD (k

Ω)

470

330

220

100

CT (pF) =

680

1000

60

70

80

90

100

RTC (k

Ω)

10

20

30

40

50

680

1000

330

470

220

100

CT (pF) =

RTD = 10k

•

•

=

A

(EQ. 1)