CS3361_15 Datasheet, PDF (7/8 Pages) ON Semiconductor – Alternator Voltage Regulator FET Driver

CS3361
REGULATION WAVEFORMS
The CS3361 utilizes proportion control to maintain
regulation. Waveforms depicting operation are shown in
Figures 4, 5 and 6, where V_BAT/N is the divided down
voltage present on the Sense pin using R1 and R2 (Figure 7).
A sawtooth waveform is generated internally. The
amplitude of this waveform is listed in the electric parameter
section as proportion control. The oscillator voltage is
summed with V_BAT/N, and compared with the internal
voltage regulator (V_REG) in the regulation comparator
which controls the field through the output “Device Driver.”
Figure 4 shows typical steady−state operation. A 50%
duty cycle is maintained.
Figure 5 shows the effect of a drop in voltage on (V_BAT/N
+ V_OSC). Notice the duty cycle increase to the field drive.
Figure 6 shows the effect of an increase in voltage (above
the regulation voltage) on (V_BAT/N + V_OSC). Notice the
decrease in field drive.
V_BAT/N + V_OSC
V_REG
V_BAT/N + V_OSC
V_REG
V_BAT/N + V_OSC
V_REG
ÌÌÌÌ
Field Driver On
Figure 4. 50% Duty Cycle,
Steady State
ÌÌÌÌ
Field Driver On
Figure 5. > 50% Duty Cycle,
Increased Load
ÌÌÌÌ
Field Driver On
Figure 6. < 50% Duty Cycle,
Decreased Load
STATOR
RECTIFIER
MR2502
MR2502
MR2502
MR2502
MR2502
MR2502
C3
0.047 μF
S
A
R1
100 kΩ
R2
50 kΩ
*C2
10 μF
R3 250 Ω
C1
0.1 μF
R4
18 kΩ
D1
MR2502
V_CC
Sense
OSC
STATORSC ^R5
F
10 kΩ
Driver
Logic level
Q1 ^{N Channel}
MTB20N20E
C4
0.022 μF
IGN
R6
20 kΩ
LAMP GND
POWER
GROUND
I
R7 10 Ω
R9
2.4 kΩ
MPSA13
*Note: C2 optional for reduced jitter.
FIELD
Lamp Indicator
R10
510 Ω
IGNITION
SWITCH
BATTERY
Figure 7. Typical Application DIagram
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