ISL6740A Datasheet, PDF (8/15 Pages) Intersil Corporation – Flexible Double-Ended Voltage-Mode PWM Controller with Voltage Feed Forward

ISL6740A
Typical Performance Curves
1.001
1
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 CT 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 (DT) vs CAPACITANCE
Pin Descriptions
V_DD - 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, Fsw, 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.
8
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
R_TC - 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. The
voltage appearing on this pin is nominally 80% of the voltage
applied to the UV/FF pin.
R_TD - 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. The
voltage appearing on this pin is nominally 80% of the voltage
applied to the UV/FF pin.
C_T - The oscillator timing capacitor is connected between
this pin and GND.
FN9195.0
February 7, 2005