UC3845AD Microsemi Analog Mixed Signal Group, UC3845AD Datasheet - Page 6
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
UC184xA/284xA/384xA
6
The RC low pass filter will eliminate the leading edge current spike
caused by parasitics of Power MOSFET.
UCx84xA
FIGURE 3. — CURRENT SENSE SPIKE SUPPRESSION
7
6
5
3
V
CC
FIGURE 5. — EXTERNAL DUTY CYCLE CLAMP AND MULTI-UNIT SYNCHRONIZATION
CHANGE
f =
f =
C
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
R
R
R
(R
A
B
A
DC BUS
A
+ 2R
R
1.44
+ 2R
B
C
T Y P I C A L A P P L I C AT I O N C I R C U I T S
Q1
R
B
U R R E N T
P
S
B
)C
7
6
2
0.01
R O D U C T I O N
Precision duty cycle limiting as well as synchronizing several parts is
possible with the above circuitry.
I
PK(MAX)
8
5
TIMER
=
555
M
1.0V
R
4
I
O D E
S
PK
1
P W M C
UCx84xA devices
3
D
A resistor (R
& ringing caused by the MOSFET input capacitance and any
inductance in series with the gate drive. (Note: It is very important to
have a low inductance ground path to insure correct operation of the
I.C. This can be done by making the ground paths as short and as
wide as possible.)
To other
A T A
O N T R O L L E R
8
4
FIGURE 4. — MOSFET PARASITIC OSCILLATIONS
1
S
) in series with the MOSFET gate will reduce overshoot
H E E T
UCx84xA
UCx84xA
5
5
7
6
V
CC
R
1
DC BUS
Q1
R
S
Copyright © 1995
Rev. 1.2a 10/25