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Unitrode |
Low Power Current Mode Push-Pull PWM
UCC1808-1/-2
UCC2808-1/-2
UCC3808-1/-2
PRELIMINARY
FEATURES
• 130µA Typical Starting
Current
• 1mA Typical Run Current
• Operation to 1MHz
• Internal Soft Start
• On Chip Error Amplifier With
2MHz Gain Bandwidth Product
• On Chip VDD Clamping
• Dual Output Drive Stages In
Push-Pull Configuration
• Output Drive Stages Capable
Of 500mA Peak Source
Current, 1A Peak Sink Current
BLOCK DIAGRAM
DESCRIPTION
The UCC3808 is a family of BiCMOS push-pull, high-speed, low power, pulse
width modulators. The UCC3808 contains all of the control and drive circuitry re-
quired for off-line or DC-to-DC fixed frequency current-mode switching power
supplies with minimal external parts count.
The UCC3808 dual output drive stages are arranged in a push-pull configura-
tion. Both outputs switch at half the oscillator frequency using a toggle flip-flop.
The dead time between the two outputs is typically 60ns to 200ns depending on
the values of the timing capacitor and resistors, thus limits each output stage
duty cycle to less than 50%.
The UCC3808 family offers a variety of package options temperature range op-
tions, and choice of undervoltage lockout levels. The family has UVLO thresh-
olds and hysteresis options for off-line and battery powered systems.
Thresholds are shown in the table below.
Part Number
UCCx808-1
UCCx808-2
Turn on Threshold
12.5V
4.3V
Turn off Threshold
8.3V
4.1V
9/97
UDG-97008
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (IDD ≤ 10mA) . . . . . . . . . . . . . . . . . . . . . . . 15V
Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA
OUTA/OUTB Source Current (peak) . . . . . . . . . . . . . . –500mA
OUTA/OUTB Sink Current (peak) . . . . . . . . . . . . . . . . 1000mA
Analog Inputs (FB, CS) –0.3V to VDD+0.3V, not to exceed 6V
Power Dissipation at TA = 25°C (N Package) . . . . . . . . . . . 1W
Power Dissipation at TA = 25°C (D Package) . . . . . . . . 650mW
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . –55°C to +150°C
Lead Temperature (Soldering, 10sec.) . . . . . . . . . . . . . +300°C
Currents are positive into, negative out of the specified terminal.
Consult Packaging Section of Databook for thermal limitations
and considerations of package.
CONNECTION DIAGRAM
DIL-8, SOIC-8 (Top View)
J or N Package, D Package
ORDER INFORMATION
UCC1808-1/-2
UCC2808-1/-2
UCC3808-1/-2
ELECTRICAL CHARACTERISTICS: Unless otherwise specified,TA = 0°C to 70°C for UCC3808-X, –40°C to 85°C for
UCC2808-X and –55°C to 125°C UCC1808-X, VDD = 10V (Note 6), 1µF capacitor from VDD to GND, Oscillator R = 22kΩ, C =
330pF. TA = TJ.
PARAMETER
TEST CONDITIONS
MIN TYP MAX UNITS
Oscillator Section
Oscillator Frequency
175 194 213 kHz
Oscillator Amplitude/VDD
(Note 1)
0.44 0.5 0.56 V/V
Error Amplifier Section
Input Voltage
COMP = 2V
1.95 2 2.05 V
Input Bias Current
–1 1 µA
Open Loop Voltage Gain
60 80
dB
COMP Sink Current
FB = 2.2V, COMP = 1V
0.3 2.5
mA
COMP Source Current
FB = 1.3V, COMP = 3.5V
–0.2 –0.5
mA
PWM Section
Maximum Duty Cycle
Measured at OUTA or OUTB
48 49 50 %
Minimum Duty Cycle
COMP = 0V
0%
Current Sense Section
Gain
(Note 2)
1.3 1.5 1.7 V/V
Maximum Input Signal
COMP = 5V (Note 3)
0.45 0.5 0.55 V
CS to Output Delay
COMP = 3.5V, CS from 0 to 600mV
100 200 ns
Input Bias Current
–200
200 nA
Over Current Threshold
0.7 0.75 0.8 V
COMP to CS Offset
CS = 0V
0.4 0.7
1
V
Output Section
OUT Low Level
I = 100mA
0.5 1
V
OUT High Level
I = –50mA, VDD – OUT
0.5 1
V
Rise Time
CL = 1nF
40 120 ns
Fall Time
CL = 1nF
20 60 ns
Undervoltage Lockout Section
Start Threshold
UCCx808-1 (Note 4)
11.5 12.5 13.5 V
UCCx808-2
4.1 4.3 4.5 V
Minimum Operating Voltage After Start
UCCx808-1 (Note 4)
7.6 8.3
9
V
UCCx808-2
3.9 4.1 4.3 V
Hysteresis
UCCx808-1
3.5 4.2 5.1 V
UCCx808-2
0.1 0.2 0.3 V
2
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