ISL6740IV-T Datasheet, PDF (10/28 Pages) Intersil Corporation – Flexible Double Ended Voltage and Current Mode PWM Controllers

ISL6740, ISL6741
Typical Performance Curves
1.001
1.000
0.999
0.998
0.997
-40 -25 -10
5 20 35 50 65 80 95 110
TEMPERATURE (°C)
FIGURE 1. REFERENCE VOLTAGE vs TEMPERATURE
65
60
55
50
45
40
0 50 100 150 200 250 300 350 400 450 500
RTD CURRENT (µA)
FIGURE 2. OSCILLATOR C_T DISCHARGE CURRENT GAIN
1•10⁴ _{CT (pF) =}
1000
680
470
1•10^{3 330}
220
100
100
10
10 20 30 40 50 60 70 80 90 100
RTD (kΩ)
FIGURE 3. DEADTIME (TD) vs CAPACITANCE
Pin Descriptions
VDD - V_DD is the power connection for the IC. To optimize noise
immunity, bypass V_DD to GND with a ceramic capacitor as close
to the V_DD and GND pins as possible.
The total supply current, I_DD, will be dependent on the load
applied to outputs OUTA and OUTB. Total I_DD current is the sum
of the quiescent current and the average output current. Knowing
the operating frequency, f_SW, and the output loading capacitance
charge, Q, per output, the average output current can be
calculated from:
I_OUT = 2 • Q • f_SW
A
(EQ. 1)
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 clock signal. The oscillator timing
capacitor, C_T, is always 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
1•10⁶
1•10⁵
RTD = 10k
CT (pF) =
100
220
680
330
1•10⁴
470
1000
10 20 30 40 50 60 70 80 90 100
RTC (kΩ)
FIGURE 4. CAPACITANCE vs FREQUENCY
clock with a pulse width less than one-half of the oscillator period
must be used.
RTC - This is the oscillator timing capacitor charge current 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.
RTD - This is the oscillator timing capacitor discharge current
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.
CT - The oscillator timing capacitor is connected between this pin
and GND.
VERROR - The inverting input of the PWM comparator. The error
voltage is applied to this pin to control the duty cycle. Increasing
the signal level increases the duty cycle. The node may be driven
with an external error amplifier or opto-coupler.
10
FN9111.6
December 2, 2011