MC34129D Freescale Semiconductor, MC34129D Datasheet - Page 12

• Manufacturer Part Number: MC34129D
• Description: IC CTLR CURRENT MODE 14-SOIC
• Manufacturer: Freescale Semiconductor

Specifications of MC34129D

• Applications: Telecommunications
• Current - Supply: 2.5mA
• Voltage - Supply: 4 V ~ 12 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: Q1707365A

12
Virtually lossless current sensing can be achieved with the implementation of a
SENSEFET power switch.
Figure 26. MOSFET Parasitic Oscillations
Series gate resistor R g will damp any high frequency parasitic
oscillations caused by the MOSFET input capacitance and any
series wiring inductance in the gate–source circuit.
Figure 24. Current Sensing Power MOSFET
Control Circuitry Ground:
1.25V
To Pin 7
+
–
9
10
11
8
1
2
3
1/4W
G
R S
3
1
2
D
M
Freescale Semiconductor, Inc.
V in
K
For More Information On This Product,
R g
To Input Source
Power Ground:
V RS
SENSEFET
S
If: SENSEFET = MTP10N10M
R S = 200
Then: V RS 0.075 I pk
Return
V in
Q1
R S
R S I pk r DS(on)
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r DM(on) + r S
MC34129 MC33129
Figure 25. Current Waveform Spike Suppression
The totem–pole output can furnish negative base current for enhanced
transistor turn–off, with the addition of capacitor C1.
The addition of the RC filter will eliminate instability caused by the
leading edge spike on the current waveform.
Figure 27. Bipolar Transistor Drive
MOTOROLA ANALOG IC DEVICE DATA
+
0
–
I B
1
2
3
1
2
3
Base Charge
C
R
Removal
V in
Q1
C1
R S
t
V in
Q1
R S