UC3845AD Microsemi Analog Mixed Signal Group, UC3845AD Datasheet - Page 7
UC3845AD
Manufacturer Part Number
UC3845AD
Description
IC CTRLR PWM CURRENT MODE 14SOIC
Manufacturer
Microsemi Analog Mixed Signal Group
Datasheet
1.UC3844AM.pdf
(8 pages)
Specifications of UC3845AD
Pwm Type
Current Mode
Number Of Outputs
1
Frequency - Max
500kHz
Duty Cycle
50%
Voltage - Supply
8.2 V ~ 25 V
Buck
Yes
Boost
Yes
Flyback
Yes
Inverting
No
Doubler
No
Divider
No
Cuk
No
Isolated
Yes
Operating Temperature
0°C ~ 70°C
Package / Case
14-SOIC (3.9mm Width), 14-SOL
Frequency-max
500kHz
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
UC3845AD1
Manufacturer:
TI
Quantity:
5 162
Part Number:
UC3845AD8TR
Manufacturer:
TI/UNITRODE
Quantity:
20 000
Company:
Part Number:
UC3845AD8TRG4
Manufacturer:
ST
Quantity:
16 109
Company:
Part Number:
UC3845ADM-TR
Manufacturer:
VIA
Quantity:
30
Company:
Part Number:
UC3845ADTR
Manufacturer:
TI
Quantity:
14 698
Copyright © 1995
Rev. 1.2a 10/25
From V
R
R
i
d
2N222A
Due to inherent instability of current mode converters running above 50% duty cycle, slope compensation should be added to either
the current sense pin or the error amplifier. Figure 6 shows a typical slope compensation technique.
High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors should be
connected to pin 5 in a single point ground. The transistor and 5k potentiometer are used to sample the oscillator waveform and apply an
adjustable ramp to pin 3.
O
R
C
SLOPE
F
C
T
ERROR AMP
ADJUST
8(14)
R
R
4(7)
2(3)
1(1)
T
F
4.7K
4.7K
1K
ERROR
OSCILLATOR
AMP
5V
ADJUST
100K
2N2222
2.5V
T Y P I C A L A P P L I C A T I O N C I R C U I T S
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
I
SENSE
5K
UVLO
C
U R R E N T
P
R O D U C T I O N
2R
FIGURE 7. — OPEN LOOP LABORATORY FIXTURE
R
T
5(9)
R
FIGURE 6. — SLOPE COMPENSATION
GOOD LOGIC
1
2
3
4
S
UCx84xA
R
COMP
V
I
R
M
1V
SENSE
V
T
FB
REF
C
T
O D E
REF
5V
UCx84xA
COMP
C.S.
C
GROUND
P W M C
T
OUTPUT
D
V
LATCH
V
PWM
REF
CC
A T A
8
7
6
5
INTERNAL
O N T R O L L E R
UC184xA/284xA/384xA
BIAS
S
0.1µF
H E E T
0.1µF
(continued)
7(12)
A
1K
7(11)
6(10)
5(8)
3(5)
V
CC
C
R
DC BUS
V
V
OUTPUT
GROUND
R
Q1
REF
CC
S
V
O
7