Texas Instruments UC3827DW-1, UC3827Q-1, UC3827N-1, UC3827N-2, UC3827DWTR-1 Datasheet
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Buck Current/Voltage Fed Push-Pull PWM Controllers
UC1827-1/-2
UC2827-1/-2
UC3827-1/-2
FEATURES
• Ideal for Multiple Output and/or High
Voltage Output Voltage Converters
• Up to 500kHz 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
Non-overlapping 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
BLOCK DIAGRAM
DESCRIPTION
The UC3827 family of controller ICs 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 guaranteed overlap period to prevent ringing and voltage stress on the devices. In the voltage fed mode, the two switches are driven with a guaranteed 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 72Vdc.
(continued)
VEA+
VEA–
CEA–
CSAO
CSA+
CSA–
SS
SYNC 19
CT
RT
REF
VCC
GND
14
16
13
7
8
9
4
18
17
15
23
11
VOLTAGE ERROR
AMPLIFIER
CURRENT
SENSE AMPLIFIER
OSC
500kHz
MAX
REF
&
UVLO
UVLO
10
+3V
ILIM
COMPARATOR
SS
UV
12
CURRENT
ERROR
AMPLIFIER
INHBT
CEAOVEAO
6 5
RAMPCEA+
0.7V
PWM
COMPARATOR
T
R
D
QS
OSC
Q
Q
DELAY
DELAY
FLYING
DRIVER
PUSH-PULL
DRIVERS
1
V+
2
BUCK
3
SRC
21
PGND
24
PUSH
22
PULL
04/99
20
DELAY
UDG-97172
DESCRIPTION (cont.)
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.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20V
Input Voltage Range
For all pins except V+, BUCK, SRC. . . . . . . . . . –0.3V to 5V
For V+ and BUCK. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90V
For SRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90V–VCC
BUCK Driver
IO Continuous. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 250mA
IO Peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 1A
PUSH/PULL Driver
IO Continuous. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 200mA
IO Peak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 0.8A
Storage Temperature . . . . . . . . . . . . . . . . . . . −65°C to +150°C
Junction Temperature. . . . . . . . . . . . . . . . . . . –55°C to +150°C
Lead Temperature (Soldering, 10 sec.). . . . . . . . . . . . . +300°C
CONNECTION DIAGRAMS
DIL-24 (Top View)
N or J, DW Packages
V+
1
2
BUCK
SRC
3
4
SS
5
RAMP
6
CEAO
7
CSAO
8
CSA+
9
CSA–
VEAO
10
11
GND
12
CEA+ CEA–
PLCC-28 (Top View)
Q Package
UC1827-1/-2
UC2827-1/-2
UC3827-1/-2
24
PUSH
VCC
23
PULL
22
PGND
21
DELAY
20
SYNC
19
CT
18
RT
17
VEA–
16
15
REF
1413VEA+
Voltages are referenced to ground. Currents are positive into,
negative out of the specified terminal. Consult Packaging
Section of Databook for thermal limitations and considerations
of packages.
TEMPERATURE AND PACKAGE
SELECTION GUIDE
TEMPERATURE
RANGE
UC1827-X –55°C to +125°C J
UC2827-X –40°C to +85°C N, DW, Q
UC3827-X 0°C to +70°C N, DW, Q
AVAILABLE
PACKAGES
PART VERSION GUIDE
PART NUMBER TOPOLOGY
UCX827-1 Current Fed Push-Pull
UCX827-2 Voltage Fed Push-Pull
ORDERING INFORMATION
UC 827
2
UC1827-1/-2
UC2827-1/-2
UC3827-1/-2
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VCC = 15V, V+ = 14.3V, CT = 340pF, RT = 10K,
RDELAY = 24.3k, SRC = GND, BUCK, PUSH and PULL outputs no load. TJ = TA.
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
Supply
VCC UVLO, Turn-On 8.3 8.8 9.5 V
Hysteresis 0.9 1.2 1.5 V
I
Start VCC = 8V 1000 µA
VCC
I
Run 32 45 mA
VCC
V+ UVLO, Turn-On 7.1 7.5 8.3 V
V+ Hysteresis 0.2 0.4 0.9 V
I
+
Buck High 0.2 1 2 mA
V
Voltage Error Amplifier
IB 0.5 3 µA
VIO 10 mV
AVOL 80 95 dB
GBW (Note 7) 1 4 MHz
VOL I
VOH I
= 0µA (No Load) 0.3 0.5 V
VEAO
= 0µA (No Load) 2.85 3 3.20 V
VEAO
Current Sense Amplifier
IB –1 –5 uA
VIO 5mV
AVOL 80 110 dB
GBW (Note 7) 15 29 MHz
VOL I
VOH I
= 0µA (No Load) 0.25 0.5 V
CEAO
= 0µA (No Load) 3 3.3 V
CEAO
Common Mode Range (Note 7) 0 2 V
Current Error Amplifier
IB –1 –5 µA
VIO 10 mV
AVOL 80 110 dB
GBW At 100kHz, Measure Gain 2 4.5 MHz
VOL I
VOH I
= 0µA (No Load) 0.25 0.5 V
CEAO
= 0µA (No Load) 3.3 3.5 V
CEAO
Common Mode Range (Note 7) 0 5 V
Oscillator Section
Frequency 180 220 250 kHz
CT Discharge Current 3.5V at CT when CT removed 5 mA
PWM Comparator
Minimum Duty Cycle 200kHz 0 %
Maximum Duty Cycle 200kHz 85 91 95 %
Buck Output Stage
Rise Time 1nF Load, (Note 3) 40 100 ns
Fall Time 1nF, Load 30 80 ns
VOH I
VOL I
= –15mA , V+ –BUCK (Note 4) 1.5 2.5 V
BUCK
I
= –150mA, V+ – BUCK (Note 4) 2 2.5 V
BUCK
= 15mA (Note 5) 0.2 0.4 V
BUCK
I
= 150mA (Note 5) 0.7 1.2 V
BUCK
3
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