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MC33065-L View Datasheet(PDF) - ON Semiconductor

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Description
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MC33065-L Datasheet PDF : 18 Pages
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MC34065H, L
Sync
Input
Capacitor CT
Latch 1
Set" Input
Compensation
1
Current Sense
1
Latch 1
Reset" Input
Drive Output 1
Drive Output
2
Enable
Latch 2
Set" Input
Compensation
2
Current Sense
2
Latch 2
Reset" Input
Drive Output 2
Figure 16. Timing
Diagram
The outputs do not contain internal current limiting,
therefore an external series resistor may be required to
prevent the peak output current from exceeding the ±400
mA maximum rating. The sink saturation (VOL) is less than
0.75 V at 50 mA.
A separate Drive Ground pin is provided and, with proper
implementation, will significantly reduce the level of
switching transient noise imposed on the control circuitry.
This becomes particularly useful when reducing the Ipk(max)
clamp level. Figure 23 shows the proper ground connections
required for current sensing power MOSFET applications.
Drive Output 2 Enable Pin
This input is used to enable Drive Output 2. Drive
Output 1 can be used to control circuitry that must run
continuously such as volatile memory and the system clock,
or a remote controlled receiver, while Drive Output 2
controls the high power circuitry that is occasionally turned
off.
Reference
The 5.0 V bandgap reference is trimmed to ±2.0%
tolerance at TJ = 25°C. The reference has short circuit
protection and is capable of providing in excess of 30 mA for
powering any additional control system circuitry.
Design Considerations
Do not attempt to construct the converter on
wirewrap or plugin prototype boards. High frequency
circuit layout techniques are imperative to prevent
pulsewidth jitter. This is usually caused by excessive noise
pickup imposed on the Current Sense or Voltage Feedback
inputs. Noise immunity can be improved by lowering circuit
impedances at these points. The printed circuit layout should
contain a ground plane with low current signal and high
current switch and output grounds returning on separate
paths back to the input filter capacitor. Ceramic bypass
capacitors (0.1 μF) connected directly to VCC and Vref may
be required depending upon circuit layout. This provides a
low impedance path for filtering the high frequency noise.
All high current loops should be kept as short as possible
using heavy copper runs to minimize radiated EMI. The
Error Amp compensation circuitry and the converter output
voltagedivider should be located close to the IC and as far
as possible from the power switch and other noise generating
components.
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