ISL6755AAZA-T Intersil, ISL6755AAZA-T Datasheet - Page 7

• Manufacturer Part Number: ISL6755AAZA-T
• Description: IC CTRLR PWM FULL-BRDG 20-QSOP
• Manufacturer: Intersil

Specifications of ISL6755AAZA-T

• Pwm Type: Voltage/Current Mode
• Number Of Outputs: 4
• Frequency - Max: 2MHz
• Duty Cycle: 100%
• Voltage - Supply: 9 V ~ 16 V
• Buck: No
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 105°C
• Package / Case: 20-QSOP
• Frequency-max: 2MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Typical Performance Curves
Pin Descriptions
VDD - VDD is the power connection for the IC. To optimize
noise immunity, bypass VDD to GND with a ceramic
capacitor as close to the VDD and GND pins as possible.
Supply voltage under-voltage lock-out (UVLO) start and stop
thresholds track each other resulting in relatively constant
hysteresis.
GND - Signal and power ground connections for this device.
Due to high peak currents and high frequency operation, a
low impedance layout is necessary. Ground planes and
short traces are highly recommended.
VREF - The 5.00V reference voltage output having 3%
tolerance over line, load and operating temperature. Bypass
to GND with a 0.1μF to 2.2μF low ESR capacitor.
CT - The oscillator timing capacitor is connected between
this pin and GND. It is charged through an internal 200μA
current source and discharged with a user adjustable current
source controlled by RTD.
RTD - This is the oscillator timing capacitor discharge
current control pin. The current flowing in a resistor
connected between this pin and GND determines the
FIGURE 1. REFERENCE VOLTAGE vs TEMPERATURE
1-10
1-10
100
1.02
1.01
0.99
0.98
10
3
4
FIGURE 3. DEADTIME (DT) vs CAPACITANCE
1
0
-40
CT = 470pF
CT = 470pF
10
-25
CT = 680pF
CT = 680pF
20
CT = 330pF
CT = 330pF
-10
30
5
TEMPERATURE (¬¨Ð
40
RTD (kΩ)
CT = 1000pF
CT = 1000pF
CT = 220pF
CT = 220pF
20
7
50
35
60
50
70
CT = 100pF
CT = 100pF
65
80
80
90 100
95 110
ISL6755
magnitude of the current that discharges CT. The CT
discharge current is nominally 20x the resistor current. The
PWM deadtime is determined by the timing capacitor
discharge duration. The voltage at RTD is nominally 2.00V.
CS - This is the input to the overcurrent comparator. The
overcurrent comparator threshold is set at 1.00V nominal.
The CS pin is shorted to GND at the termination of either
PWM output.
Depending on the current sensing source impedance, a
series input resistor may be required due to the delay
between the internal clock and the external power switch.
This delay may result in CS being discharged prior to the
power switching device being turned off.
RAMP - This is the input for the sawtooth waveform for the
PWM comparator. The RAMP pin is shorted to GND at the
termination of the PWM signal. A sawtooth voltage
waveform is required at this input. For current-mode control
this pin is connected to CS and the current loop feedback
signal is applied to both inputs. For voltage-mode control,
the oscillator sawtooth waveform may be buffered and used
to generate an appropriate signal, RAMP may be connected
to the input voltage through a RC network for voltage feed
forward control, or RAMP may be connected to VREF
FIGURE 2. CT DISCHARGE CURRENT GAIN vs RTD CURRENT
1-10
100
10
3
0.1
25
24
23
22
21
20
19
18
FIGURE 4. CAPACITANCE vs FREQUENCY
RTD = 10kΩ
0
RTD = 50kΩ
200
RTD = 100kΩ
RTD CURRENT (¬¨¬
400
CT (nF)
1
600
800
September 29, 2008
1000
FN6442.1
10