RC4190
PRODUCT SPECIFICATION
1.4V
0.5V
C
A
B
C
D
X
(Internal)
OSC
I
I
(Max)
LOAD
L
0mA
0.72V
(Internal)
V
BEQ1
0V
V
V
– V
BAT
OUT BAT
L
L
X
I
X
MAX
I
I
LX
E
F
0 mA
I
MAX
D
0 mA
V
V
+ V
V
LX
OUT
MAX
D
G
0.3V (Q1 SAT)
65-2674
Figure 8. Step-Up Regulator Waveforms
+VS
R1
1M
Motorola
MBR140P
R4
R5
VOUT
6
5
+VS
CT*
1 µF
Q1
TIP73
IC
R2
Q2
2N3904
7
LX
VFB
4190
CF
GND
3
C
X
R3
2
C
X
65-2675
50 V
S
R5 =
R4 = 10 R5
* May not be required
I
MAX
Figure 9. High Power Step-Up Regulator
(With the addition of a power transistor (TIP73) and a few components, the 4190 can accomodate load power up to 10W.)
At this point, the feedback (pin 7) senses that the output volt-
age is too low, by comparing a division of the output voltage
(set by the ratio of R2 to R3) to the +1.31V reference. If the
output voltage is too low then the comparator output changes
to a logical zero. The NOR gate then effectively ANDs the
oscillator square wave with the comparator signal; if the
comparator output is zero AND the oscillator output is low,
then the NOR gate output is high and the switch transistor
will be forced on. When the oscillator goes high again, the
NOR gate output goes low and the switch transistor will turn
off. This turning on and off of the switch transistor performs
the same function that opening and closing the switch in the
simple DC-to-DC Converter does; i.e., it stores energy in the
inductor during the on time and releases it into the capacitor
during the off time.
The comparator will continue to allow the oscillator to turn
the switch on and off until enough charge has been delivered
to the capacitor to raise the feedback voltage above 1.31V.
Thereafter, this feedback system will vary the duration of the
on time in response to changes in load current or battery
7
RAYTHEON [ RAYTHEON COMPANY ]
