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UC3886 Datasheet Preview

UC3886 Datasheet

Average Current Mode PWM Controller IC

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UC3886 pdf
Average Current Mode PWM Controller IC
UC1886
UC2886
UC3886
FEATURES
10.3V - 20V Operating Range
Low Offset Voltage Amplifier
High Bandwidth Current and Voltage
Amplifiers
Low Offset Current Sense Amplifier
Undervoltage Lockout
Trimmed 5 Volt Reference
Externally Programmable Oscillator
Charge Current
1.5A Peak Totem Pole Output
Available in 16-pin DIL or SOIC
Packages
BLOCK DIAGRAM
DESCRIPTION
The UC3886 family of PWM controller ICs is designed for DC-to-DC con-
verters with average current mode control. It is designed for use in con-
junction with the UC3910 4-bit DAC and Voltage Monitor. The UC3886
drives an external N-channel MOSFET and can be used to power the In-
tel Pentium® Pro and other high-end microprocessors.
The UC3886 in conjunction with the UC3910 converts 5VDC to an adjust-
able output ranging from 2.0V to 3.5V in 100mV steps with 35mV DC sys-
tem accuracy.
The oscillator is programmed by the user’s selection of an external resis-
tor and capacitor, and is designed for 300kHz typical operation.
The voltage and current amplifiers have 3.5MHz gain-bandwidth product
to satisfy high performance system requirements.
The internal current sense amplifier permits the use of a low value current
sense resistor, minimizing power loss. It has inputs and outputs accessi-
ble to allow user-selection of gain-setting resistors, and is internally com-
pensated for a gain of 5 and above. The command voltage input is
buffered and provided for use as the reference for the current sense am-
plifier.
The output of the voltage amplifier (input to the current amplifier) is
clamped to 1 volt above the command voltage to serve as a current limit.
The gate output can be disabled by bringing the CAO/ENBL pin to below
0.8 volts.
6/98
UDG-95098-2



Unitrode
Unitrode

UC3886 Datasheet Preview

UC3886 Datasheet

Average Current Mode PWM Controller IC

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UC3886 pdf
ABSOLUTE MAXIMUM RATINGS
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20V
Output Current
CAM, COMMAND, VSENSE, ISN, ISP . . . . . . . . . . . . . ± 1A
Analog Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to 7V
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . –55°C to +150°C
Lead Temperatue (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C
Currents are positive into, negative out of the specified terminal.
Consult Packaging Section of Databook for thermal limitations
and considerations of packages.
CONNECTION DIAGRAM
DIL-16, SOIC-16 (Top View)
J, N, or D Packages
UC1886
UC2886
UC3886
ELECTRICAL CHARACTERISTICS Unless otherwise specified, VCC = 12V, VCOMMAND = 3.0V, CT = 1nF, RT = 10k,
TA = TJ = 0°C < TA < 70°C for the UC3886. (Note: –25°C < TA < 85°C for the UC2886, and –55°C < TA < 125°C for the UC1886)
PARAMETER
TEST CONDITIONS
MIN TYP MAX UNITS
Overall
Supply Current
VCC = 11V, Gate Open
10 15 mA
VCC = 9.3V
5 mA
Undervoltage Lockout
Start Threshold
9.7 10.3 10.8 V
UVLO Hysteresis
0.25 0.4
V
Voltage Error Amplifier
Input Offset Voltage
Input Bias Current
Input Offset Current
Open Loop Gain
VCM = 3.0V (UC3886)
VCM = 3.0V (UC2886, UC1886)
VCM = 3.0V
VCM = 3.0V (UC3886)
VCM = 3.0V (UC2886, UC1886)
2.5V < VCOMP < 3.5V
4 mV
15 mV
2 µA
0.01 µA
0.1 µA
60 85
dB
Common-Mode Rejection Ratio
Power Supply Rejection Ratio
2V < VCOMP < 4V
11V < VCC < 15V
60 85
60 85
dB
dB
Output High Voltage (Clamp)
Output Low Voltage (Clamp)
Output Sink Current
Output Source Current
Gain-Bandwidth Product
ICOMP = –100µA (UC3886)
ICOMP = –100µA (UC2886, UC1886)
ICOMP = 100µA
VCOMP = 3.7V
VCOMP = 2.8V
F = 100kHz
3.95
3.9
1.9
0.9
–0.15
2
4
0.25
3.5
4.05
4.1
2.7
V
V
V
mA
mA
MHz
5.0V Reference
Output Voltage
Total Variation
IVREF = 1.0mA
Line, Load, Temperature
4.9 5 5.1 V
4.825
5.175 V
Line Regulation
11V < VCC < 15V
10 mV
Load Regulation
Short Circuit Current
0 < IVREF < 2mA
15 mV
–10 40 mA
2


Part Number UC3886
Description Average Current Mode PWM Controller IC
Maker Unitrode
Total Page 8 Pages
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