UC2845BD1G ON Semiconductor, UC2845BD1G Datasheet - Page 6
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UC2845BD1G
Manufacturer Part Number
UC2845BD1G
Description
IC CTRLR CURRENT MODE HP 8-SOIC
Manufacturer
ON Semiconductor
Datasheet
1.UC3844BDR2G.pdf
(19 pages)
Specifications of UC2845BD1G
Pwm Type
Current Mode
Number Of Outputs
1
Frequency - Max
275kHz
Duty Cycle
50%
Voltage - Supply
8.2 V ~ 25 V
Buck
No
Boost
Yes
Flyback
Yes
Inverting
Yes
Doubler
No
Divider
No
Cuk
No
Isolated
Yes
Operating Temperature
-25°C ~ 85°C
Package / Case
8-SOIC (3.9mm Width)
Frequency-max
275kHz
Duty Cycle (max)
48 % (Typ)
Output Voltage
4.95 V to 5.05 V
Output Current
1000 mA (Max)
Mounting Style
SMD/SMT
Switching Frequency
500 KHz
Operating Supply Voltage
30 V
Maximum Operating Temperature
85 C
Fall Time
50 ns
Minimum Operating Temperature
- 25 C
Rise Time
50 ns
Synchronous Pin
No
Topology
Boost or Flyback
Rohs Compliant
YES
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
PIN FUNCTION DESCRIPTION
8−Pin
- 2.0
-1.0
3.0
2.0
1.0
1
2
3
4
5
6
7
8
0
0
0
Pin
Ä Ä
2,4,6,13
14−Pin
V
CC
Ä Ä Ä Ä
Ä Ä Ä Ä
Figure 14. Output Cross Conduction
Figure 12. Output Saturation Voltage
10
12
14
11
1
3
5
7
8
9
T
A
Ä Ä Ä
Ä Ä Ä
T
= - 55°C
A
200
= 25°C
Compensation
Current Sense
I
O
versus Load Current
, OUTPUT LOAD CURRENT (mA)
Feedback
Function
Voltage
Ground
Output
Power
R
Ä Ä Ä Ä Ä
Ä Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä Ä
Ä Ä Ä Ä Ä
GND
GND
V
V
NC
T
V
CC
ref
/C
C
Source Saturation
(Load to Ground)
Sink Saturation
(Load to V
T
T
100 ns/DIV
A
= - 55°C
400
CC
This pin is the Error Amplifier output and is made available for loop compensation.
This is the inverting input of the Error Amplifier. It is normally connected to the switching power
supply output through a resistor divider.
A voltage proportional to inductor current is connected to this input. The PWM uses this
information to terminate the output switch conduction.
The Oscillator frequency and maximum Output duty cycle are programmed by connecting resistor
R
This pin is the combined control circuitry and power ground.
This output directly drives the gate of a power MOSFET. Peak currents up to 1.0 A are sourced
and sunk by this pin. The output switches at one−half the oscillator frequency.
This pin is the positive supply of the control IC.
This is the reference output. It provides charging current for capacitor C
This pin is a separate power ground return that is connected back to the power source. It is used
to reduce the effects of switching transient noise on the control circuitry.
The Output high state (V
connection, it can reduce the effects of switching transient noise on the control circuitry.
This pin is the control circuitry ground return and is connected back to the powersource ground.
No connection. These pins are not internally connected.
)
T
to V
Ä Ä Ä Ä Ä
Ä Ä Ä Ä Ä
Ä Ä Ä
ref
V
80 ms Pulsed Load
120 Hz Rate
GND
Ä Ä Ä Ä
Ä Ä Ä Ä
CC
600
and capacitor C
= 15 V
T
A
V
C
T
A
CC
= 25°C
L
= 25°C
= 15 pF
= 30 V
http://onsemi.com
800
OH
T
) is set by the voltage applied to this pin. With a separate power source
to ground. Oscillator operation to 1.0 kHz is possible.
6
90
10
%
%
25
20
15
10
5
0
Figure 15. Supply Current versus Supply Voltage
0
Description
Figure 13. Output Waveform
10
V
CC
, SUPPLY VOLTAGE (V)
50 ns/DIV
20
T
through resistor R
Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä
Ä Ä Ä Ä
R
C
V
I
T
Sense
A
FB
T
T
= 25°C
= 10 k
= 3.3 nF
= 0 V
30
V
C
T
= 0 V
A
CC
L
= 25°C
= 1.0 nF
= 15 V
T
.
40