Texas Instruments UC2866N, UC2868N, UC2864QTR, UC2864Q, UC2864DWTR Datasheet

UC1861-1868
UC2861-2868
UC3861-3868

10/98

FEATURES

• Controls Zero Current Switched (ZCS)
or Zero Voltage Switched (ZVS)
Quasi-Resonant Converters

• Zero-Crossing Terminated One-Shot
Timer

• Precision 1%, Soft-Started 5V
Reference

• Programmable Restart Delay
Following Fault

• Voltage-Controlled Oscillator (VCO)
with Programmable Minimum and
Maximum Frequencies from 10kHz to
1MHz

• Low Start-Up Current (150µA typical)

• Dual 1 Amp Peak FET Drivers

• UVLO Option for Off-Line or DC/DC

Applications

DESCRIPTION

The UC1861-1868 family of ICs is optimized for the control of Zero Cur­rent Switched and Zero Voltage Switched quasi-resonant converters. Dif­ferences between members of this device family result from the various
combinations of UVLO thresholds and output options. Additionally, the
one-shot pulse steering logic is configured to program either on-time for
ZCS systems (UC1865-1868), or off-time for ZVS applications (UC1861-

1864).
The primary control blocks implemented include an error amplifier to com-

pensate the overall system loop and to drive a voltage controlled oscillator
(VCO), featuring programmable minimum and maximum frequencies. Trig­gered by the VCO, the one-shot generates pulses of a programmed maxi­mum width, which can be modulated by the Zero Detection comparator.
This circuit facilitates “true” zero current or voltage switching over various
line, load, and temperature changes, and is also able to accommodate the
resonant components' initial tolerances.

Under-Voltage Lockout is incorporated to facilitate safe starts upon
power-up. The supply current during the under-voltage lockout period is
typically less than 150µA, and the outputs are actively forced to the low
state. (continued)

BLOCK DIAGRAM

Resonant-Mode Power Supply Controllers

UDG-92018

Pin numbers refer to the J and N packages.

Device 1861 1862 1863 1864 1865 1866 1867 1868

UVLO

16.5/10.5 16.5/10.5 36014 36014 16.5/10.5 16.5/10.5 36014 36014

Outputs

Alternating Parallel Alternating Parallel Alternating Parallel Alternating Parallel

“Fixed”

Off Time Off Time Off Time Off Time On Time On Time On Time On Time

2

UC1861-1868
UC2861-2868
UC3861-3868

ABSOLUTE MAXIMUM RATINGS

VCC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22V

Output Current

Source or Sink (Pins 11 & 14) . . . . . . . . . . . . . . . . . . . . . 0.5A

DC Pulse (0.5µs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5A

Power Ground Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . .±0.2V

Inputs (Pins 2, 3, 10, & 15) . . . . . . . . . . . . . . . . . . . . –0.4 to 7V

Error Amp Output Current . . . . . . . . . . . . . . . . . . . . . . . .±2mA

Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W

Junction Temperature (Operating). . . . . . . . . . . . . . . . . . 150°C

Lead Temperature (Soldering, 10 seconds) . . . . . . . . . . 300°C

All voltages are with respect to signal ground and all currents
are positive into the specified terminal. Pin numbers refer to
the J and N packages. Consult Unitrode Integrated Circuits da­tabook for information regarding thermal specifications and
limitations of packages.

DIL-16, SOIC-16 (Top View)
J or N, DW Packages

CONNNECTION DIAGRAMS

PLCC-20 & LCC-20 (Top View)
Q & L Package

DESCRIPTION (cont.)

UVLO thresholds for the UC1861/62/65/66 are 16.5V
(ON) and 10.5V (OFF), whereas the UC1863/64/67/68
thresholds are 8V (ON) and 7V (OFF). After V

CC

ex­ceeds the UVLO threshold, a 5V generator is enabled
which provides bias for the internal circuits and up to
10mA for external usage.

A Fault comparator serves to detect fault conditions and
set a latch while forcing the output drivers low. The Soft­Ref pin serves three functions: providing soft start, re-

start delay, and the internal system reference.
Each device features dual 1 Amp peak totem pole output

drivers for direct interface to power MOSFETS. The out­puts are programmed to alternate in the
UC1861/63/65/67 devices. The UC1862/64/66/68 out­puts operate in unison alllowing a 2 Amp peak current.

PACKAGE PIN FUNCTION

FUNCTION PIN

Soft Ref 1
5V 2
NI 3
INV 4
E/A Out 5
Sig Gnd 6
Range 7
R

MIN 8

C

VCO 9

RC 10
Zero 11
NC 12
NC 13
A Out 14
Pwr Gnd 15
Pwr Gnd 16
V

CC 17

B Out 18

3

UC1861-1868
UC2861-2868
UC3861-3868

ELECTRICAL CHARACTERISTICS

Unless otherwise stated, all specifications apply for –55°C≤TA≤125°C for the
UC186x, –25°C≤TA≤85°C for the UC286x, and 0°C≤TA≤70°C for the UC386x, VCC=12V, CVCO=1nF, Range=7.15k, RMIN=86.6k,
C=200pF, R=4.02k, and Csr=0.1µF. TA=TJ .

PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

5V Generator

Output Voltage 12V ≤ Vcc≤ 20V, –10mA ≤ I

O ≤ 0mA 4.8 5.0 5.2 V

Short Circuit Current V

O = 0V –150 –15 mA

Soft-Reference

Restart Delay Current V = 2V 10 20 35 µA
Soft Start Current V = 2V –650 –500 –350 µA
Reference Voltage T

J = 25°C, IO = 0A 4.95 5.00 5.05 V

12V ≤ V

CC ≤ 20V, –200µA ≤ IO ≤ 200µA 4.85 5.15 V

Line Regulation 12V ≤ V

CC ≤ 20V 2 20 mV

Load Regulation –200µA ≤ I

O ≤ 200µA1030mV

Error Amplifier (Note 3)

Input Offset Voltage V

CM = 5V, Vo = 2V, IO = 0A –10 10 mV

Input Bias Current V

CM = 0V –2.0 –0.3 µA

Voltage Gain Vcm = 5V, 0.5V ≤ V

O ≤ 3.7V, IO = 0A 70 100 dB

Power Supply Rejection Ratio Vcm = 5V, V

O = 2V, 12V ≤ VCC ≤ 20V 70 100 dB

Error Amplifier (Note 3) (cont.)

Common Mode Rejection Ratio 0V ≤ Vcm ≤ 6V, V

O = 2V 65 100 dB

V

OUT Low VID = –100mV, IO = 200µA 0.17 0.25 V

V

OUT High VID = 100mV, IO = –200µA 3.9 4.2 V

Unity Gain Bandwidth (Note 4) 0.5 0.8 MHz

Voltage Controlled Oscillator

Maximum Frequency V

ID (Error Amp) = 100mV, TJ = 25°C 450 500 550 kHz

V

ID (Error Amp) = 100mV 425 575 kHz

Minimum Frequency V

ID (Error Amp) = –100mV, TJ = 25°C 45 50 55 kHz

V

ID (Error Amp) = –100mV 42 58 kHz

One Shot

Zero Comparator Vth 0.45 0.50 0.55 V
Propagation Delay (Note 4) 120 200 ns
Maximum Pulse Width V

ZERO = 1V 850 1000 1150 ns

Maximum to Minimum Pulse V

ZERO = 0V UCx861 – UCx864 2.5 4 5.5

Width Ratio V

ZERO = 0V UCx865 – UCx868. –55°C to +85°C 4 5.5 7

V

ZERO = 0V UCx865 – UCx868, +125°C 3.8 5.5 7

Output Stage

Rise and Fall Time C

LOAD = 1nF (Note 4) 25 45 ns

Output Low Saturation I

O = 20mA 0.2 0.5 V

I

O = 200mA 0.5 2.2 V

Output High Saturation I

O = –200mA, down from Vcc 1.7 2.5 V

UVLO Low Saturation I

O = 20mA 0.8 1.5 V

Fault Comparator

Fault Comparator Vth 2.85 3.00 3.15 V
Delay to Output (Note 4) (Note 5) 100 200 ns