CONTROLLERS. UC2827-2 Datasheet

UC2827-2 Datasheet PDF


Part

UC2827-2

Description

BUCK CURRENT/VOLTAGE FED PUSH-PULL PWM CONTROLLERS

Manufacture

etcTI

Page 16 Pages
Datasheet
Download UC2827-2 Datasheet


UC2827-2 Datasheet
UC2827-1, UC2827-2
UC3827-1, UC3827-2
www.ti.com
SLUS365D APRIL 1999 REVISED APRIL 2011
BUCK CURRENT/VOLTAGE FED PUSH-PULL
PWM CONTROLLERS
Check for Samples: UC2827-1, UC2827-2, UC3827-1, UC3827-2
FEATURES
1
Ideal for Multiple Output and/or High
Voltage Output Voltage Converters
Up to 500 kHz Operation
High Voltage, High Current Floating
Driver for Buck Converter Stage
UC3827-1 Current Fed Controller has
Push-Pull Drivers with Overlapping
Conduction Periods
UC3827-2 Voltage Fed Controller has
Push-Pull Drivers with Nonoverlapping
Conduction Periods
Average Current Mode, Peak Current
Mode or Voltage Mode with Input
Voltage Feedforward Control for Buck
Power Stage
Wide Bandwidth, Low Offset,
Differential Current Sense Amplifier
Precise Short Circuit Current Control
DESCRIPTION
The UC3827 family of controller devices provides an
integrated control solution for cascaded buck and
push-pull converters. These converters are known as
current fed or voltage fed push-pull converters and
are ideally suited for multiple output and/or high
voltage output applications. In both current fed and
voltage fed modes, the push-pull switches are driven
at 50% nominal duty cycles and at one half the
switching frequency of the buck stage. In the current
fed mode, the two switches are driven with a
specified over-lap period to prevent ringing and
voltage stress on the devices. In the voltage fed
mode, the two switches are driven with a specified
gap time between the switches to prevent shorting
the transformer across the energy storage capacitor
and to prohibit excessive currents flowing through the
devices.
The converter's output voltage is regulated by pulse
width modulation of the buck switch. The UC3827
contains complete protection and PWM control
functions for the buck converter. Easy control of the
floating switch is accomplished by the floating drive
circuitry. The gate drive waveform is level shifted to
support an input voltage up to 72 VDC.
BLOCK DIAGRAM
VEAOCEA+ CEAO
10
Voltage Error
Amplifier
VEA+ 14
12
6
VEA− 16
Current Error
Amplifier
CEA− 13
CSAO 7
CSA+ 8
CSA− 9
SS 4
SYNC 19
CT 18
RT 17
+3 V
ILIM Comparator
Current Sense
Amplifier
OSC
SS
INHBT
UV
500 kHz
MAX
REF 15
RAMP
5
0.7 V PWM Comparator
RD
SQ
OSC
Q DELAY
T
Q
VCC 23
GND 11
REF
&
UVLO UVLO
DELAY
Flying
Driver
Push/Pull
Drivers
20
DELAY
1 V+
2 BUCK
3 SRC
21 PGND
24 PUSH
22 PULL
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 19992011, Texas Instruments Incorporated

UC2827-2 Datasheet
UC2827-1, UC2827-2
UC3827-1, UC3827-2
SLUS365D APRIL 1999 REVISED APRIL 2011
www.ti.com
DESCRIPTION (CONTINUED)
The UC3827 can be set up in traditional voltage mode control using input voltage feedforward technique or in
current mode control. Using current mode control prevents potential core saturation of the push-pull transformer
due to mismatches in timing and in component tolerances. With average current mode control, precise control of
the inductor current feeding the push-pull stage is possible without the noise sensitivity associated with peak
current mode control. The UC3827 average current mode loop can also be connected in parallel with the voltage
regulation loop to assist only in fault conditions.
Other valuable features of the UC3827 include bidirectional synchronization capability, user programmable
overlap time (UC3827-1), user programmable gap time (UC3827-2), a high bandwidth differential current sense
amplifier, and soft start circuitry.
TA = TJ
-40°C to 85°C
0°C to 70°C
ORDERING INFORMATION(1)
PUSH-PULL TOPOLOGY
Current Fed
Voltage Fed
Current Fed
Voltage Fed
SOIC-24
UC2827DW-1
UC2827DW-2
UC3827DW-1
UC3827DW-2
PACKAGES
PDIP-24
UC2827N-1
UC2827N-2
UC3827N-1
UC3827N-2
PLCC-28
-
-
UC3827Q-1
-
(1) The DW and Q packages are also available taped and reeled. Add a TR suffix to the device type (i.e., UC2827DWTR-1).
THERMAL INFORMATION
THERMAL METRIC
UC2827-1,
UC2827-2,
UC3827-1,
UC3827-2
UC2827-1,
UC2827-2,
UC3827-1,
UC3827-2
UNITS
NJ
θJA
θJCtop
Junction-to-ambient thermal resistance(1)
Junction-to-case (top) thermal resistance(2)
24 PINS
60
30
24 PINS
70 to 80
28
°C/W
(1) The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, high-K board, as
specified in JESD51-7, in an environment described in JESD51-2a.
(2) The junction-to-case (top) thermal resistance is obtained by simulating a cold plate test on the package top. No specific
JEDEC-standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.
THERMAL INFORMATION
THERMAL METRIC
UC2827-1,
UC2827-2,
UC3827-1,
UC3827-2
DW
UC2827-1,
UC2827-2,
UC3827-1,
UC3827-2
(1)QLCC
UNITS
θJA
θJCtop
Junction-to-ambient thermal resistance(2)
Junction-to-case (top) thermal resistance(3)
28 PINS
71 to 83
24
28 PINS
40 to 65
30
°C/W
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
(2) The junction-to-ambient thermal resistance under natural convection is obtained in a simulation on a JEDEC-standard, high-K board, as
specified in JESD51-7, in an environment described in JESD51-2a.
(3) The junction-to-case (top) thermal resistance is obtained by simulating a cold plate test on the package top. No specific
JEDEC-standard test exists, but a close description can be found in the ANSI SEMI standard G30-88.
2 Copyright © 19992011, Texas Instruments Incorporated


Features Datasheet pdf UC2827-1, UC2827-2 UC3827-1, UC3827-2 w ww.ti.com SLUS365D – APRIL 1999 – REVISED APRIL 2011 BUCK CURRENT/VOLTAGE FED PUSH-PULL PWM CONTROLLERS Check fo r Samples: UC2827-1, UC2827-2, UC3827-1 , UC3827-2 FEATURES 1 • Ideal for Mu ltiple Output and/or High Voltage Outpu t Voltage Converters • Up to 500 kHz Operation • High Voltage, High Curren t Floating Driver for Buck Converter St age • UC3827-1 Current Fed Controller has Push-Pull Drivers with Overlapping Conduction Periods • UC3827-2 Voltag e Fed Controller has Push-Pull Drivers with Nonoverlapping Conduction Periods • Average Current Mode, Peak Current Mode or Voltage Mode with Input Voltage Feedforward Control for Buck Power Sta ge • Wide Bandwidth, Low Offset, Diff erential Current Sense Amplifier • Pr ecise Short Circuit Current Control DE SCRIPTION The UC3827 family of controll er devices provides an integrated contr ol solution for cascaded buck and push- pull converters. These converters are known as current fed or voltage fed push-pull.
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