TI UC1833

UC1832/3
UC2832/3
UC3832/3
Precision Low Dropout Linear Controllers
FEATURES
DESCRIPTION
•
Precision 1% Reference
•
Over-Current Sense Threshold
Accurate to 5%
•
Programmable Duty-Ratio
Over-Current Protection
•
4.5V to 36V Operation
•
100mA Output Drive, Source or
Sink
•
Under-Voltage Lockout
The UC1832 and UC1833 series of precision linear regulators include all the
control functions required in the design of very low dropout linear regulators.
Additionally, they feature an innovative duty-ratio current limiting technique
which provides peak load capability while limiting the average power dissipation of the external pass transistor during fault conditions. When the load current reaches an accurately programmed threshold, a gated-astable timer is
enabled, which switches the regulator’s pass device off and on at an externally
programmable duty-ratio. During the on-time of the pass element, the output
current is limited to a value slightly higher than the trip threshold of the duty-ratio timer. The constant-current-limit is programmable on the UCx832 to allow
higher peak current during the on-time of the pass device. With duty-ratio control, high initial load demands and short circuit protection may both be accommodated without extra heat sinking or foldback current limiting. Additionally, if
the timer pin is grounded, the duty-ratio timer is disabled, and the IC operates
in constant-voltage/constant-current regulating mode.
Additional Features of the UC1832
series:
•
Adjustable Current Limit to
Current Sense Ratio
•
Separate +VIN terminal
•
Programmable Driver Current
Limit
•
Access to VREF and E/A(+)
•
Logic-Level Disable Input
These IC’s include a 2 Volt (±1%) reference, error amplifier, UVLO, and a high
current driver that has both source and sink outputs, allowing the use of either
NPN or PNP external pass transistors. Safe operation is assured by the inclusion of under-voltage lockout (UVLO) and thermal shutdown.
The UC1833 family includes the basic functions of this design in a low-cost, 8pin mini-dip package, while the UC1832 series provides added versatility with
the availability of 14 pins. Packaging options include plastic (N suffix), or ceramic (J suffix). Specified operating temperature ranges are: commercial (0°C
to 70°C), order UC3832/3 (N or J); industrial (–25°C to 85°C), order UC2832/3
(N or J); and military (–55°C to 125°C), order UC1832/3J. Surface mount
packaging is also available.
BLOCK DIAGRAMS
UDG-92040
6/94
UC1832/3
UC2832/3
UC3832/3
ABSOLUTE MAXIMUM RATINGS
Supply Voltage +VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40V
Driver Output Current (Sink or Source) . . . . . . . . . . . . . 450mA
Driver Sink to Source Voltage . . . . . . . . . . . . . . . . . . . . . . . 40V
TRC Pin Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to 3.2V
Other Input Voltages. . . . . . . . . . . . . . . . . . . . . . . –0.3V to +VIN
Operating Junction Temperature (note 2) . . . –55°C to +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) . . . . . . . . . . 300°C
Note 1: Unless otherwise indicated, voltages are referenced to
ground and currents are positive into, negative out of, the specified terminals.
Note 2: See Unitrode Integrated Circuits databook for
information regarding thermal specifications and limitations of
packages.
CONNECTION DIAGRAMS
UC1832
UC1833
DIL-14 (Top View)
J Or N Package
DIL-8 (Top View)
J Or N Package
SOIC-16 (Top View)
DW Package
SOIC-16 (Top View)
DW Package
LCC-20 & PLCC-20
L & Q Package
(Top View)
PACKAGE PIN FUNCTION
FUNCTION
N/C
+VIN
Comp/Shutdown
E/A(+)
+2V REF
N/C
Gnd
Logic Disable
Limit
Source
N/C
E/A(-)
Sink
VADJ
N/C
Timer RC
Current Sense(-)
Current Sense(+)
LCC-20 & PLCC-20
L & Q Package
(Top View)
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15-17
18
19
20
2
PACKAGE PIN FUNCTION
FUNCTION
+VIN & C/S(+)
N/C
N/C
N/C
Comp/Shutdown
Gnd
N/C
N/C
N/C
Source
N/C
E/A(-)
N/C
N/C
Sink
Timer RC
Current Sense(+)
N/C
PIN
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18-20
UC1832/3
UC2832/3
UC3832/3
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, specifications hold for TA = 0°C to 70°C for the
UC3832/3, –25°C to 85°C for the UC2832/3, and –55°C to 125°C for the
UC1832/3, +VIN = 15V, Driver sink = +VIN, C/S(+) voltage = +VIN. TA=TJ.
PARAMETER
Input Supply
Supply Current
TEST CONDITIONS
MIN
TYP
MAX
UNITS
+VIN = 6V
6.5
10
mA
+VIN = 36V
9.5
15
mA
Logic Disable = 2V (UCx832 only)
3.3
mA
Reference Section
Output Voltage (Note 3)
Load Regulation (UCx832 only)
Line Regulation
TJ = 25°C, IDRIVER = 10mA
1.98
2.00
2.02
V
over temperature, IDRIVER = 10mA
1.96
2.00
2.04
V
IOUT = 0 to 10mA
+VIN = 4.5 to 36V, IDRIVER = 10mA
-10
-5.0
0.033
0.5
mV
mV/V
3.6
4.5
V
1.5
Under-Voltage Lockout Threshold
Logic Disable Input (UCx832 only)
Threshold Voltage
Input Bias Current
Logic Disable = 0V
1.3
1.4
-5.0
-1.0
V
95
100
105
mV
93
110
100
135
107
170
mV
mV
µA
Current Sense Section
Comparator Offset
Over Temperature
Amplifier Offset (UCx833 only)
Amplifier Offset (UCx832 only)
VADJ = Open
110
135
170
mV
VADJ = 1V
180
235
290
mV
VADJ = 0V
250
305
360
mV
Input Bias Current
VCM = +VIN
65
100
135
µA
Input Offset Current (UCx832 only)
VCM = +VIN
-10
10
µA
Amplifier CMRR (UCx832 only)
Transconductance
VCM = 4.1V to +VIN+0.3V
ICOMP = ±100µA
VADJ Input Current (UCx832 only)
VADJ = 0V
80
dB
-10
65
-1
mS
µA
0.25
1.0
µA
-345
-270
-175
µA
Timer
Inactive Leakage Current
C/S(+) = C/S(-) = +VIN; TRC pin = 2V
Active Pullup Current
C/S(+) = +VIN, C/S(-) = +VIN - 0.4V; TRC pin = 0V
Duty Ratio (note 4)
ontime/period, RT = 200k, CT = 0.27µF
4.8
%
Period (notes 4,5)
ontime + offtime, RT = 200k, CT = 0.27µF
36
ms
Upper Trip Threshold (Vu)
1.8
V
Lower Trip Threshold (Vl)
Trip Threshold Ratio
0.9
2.0
V
V/V
Vu/Vl
Error Amplifier
Input Offset Voltage (UCx832 only)
VCM = VCOMP = 2V
-8.0
Input Bias Current
VCM = VCOMP = 2V
-4.5
Input Offset Current (UCx832 only)
VCM = VCOMP = 2V
-1.5
AVOL
VCOMP = 1V to 13V
50
70
dB
CMRR (UCx832 only)
VCM = 0V to +VIN - 3V
60
80
dB
PSRR (UCx832 only)
Transconductance
VCM = 2V, +VIN = 4.5 to 36V
ICOMP = ±10µA
90
4.3
dB
mS
VOH
ICOMP = 0, Volts below +VIN
.95
1.3
V
VOL
ICOMP = 0
.45
0.7
V
IOH
VCOMP = 2V
-500
-100
µA
-700
3
8.0
mV
µA
-1.1
1.5
µA
UC1832/3
UC2832/3
UC3832/3
Unless otherwise stated, specifications hold for TA = 0°C to 70°C for the UC3832/3, –25°C to
ELECTRICAL
CHARACTERISTICS (cont.) 85°C for the UC2832/3, and –55°C to 125°C for the UC1832/3, +VIN = 15V, Driver sink =
+VIN, C/S(+) voltage = +VIN. TA=TJ.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNITS
VCOMP = 2V, C/S(-) = +VIN
VCOMP = 2V, C/S(-) = +VIN - 0.4V
100
500
700
2
6
Driver Limit & Source pins common; TJ = 25°C
200
300
400
mA
Over Temperature
100
300
450
mA
Error Amplifier (cont.)
IOL
µA
mA
Driver
Maximum Current
Limiting Voltage (UCx832 only)
Driver Limit to Source voltage at current limit,
Internal Current Sense Resistance
Pull-Up Current at Driver Sink
ISOURCE = -10mA; TJ = 25°C (Note 6)
.72
V
TJ = 25°C (Note 6)
2.4
Ω
Compensation/Shutdown = 0.4V; Driver Sink = +VIN - 1V
-100
µA
-300
-75
µA
300
700
µA
-800
-300
-1000
150
Compensation/Shutdown = 0.4V, +VIN = 36V; Driver
Sink = 35V
Pull-Down Current at Driver Source
Compensation/Shutdown = 0.4V; Driver Source = 1V
Saturation Voltage Sink to Source
Driver Source = 0V; Driver Current = 100mA
Maximum Source Voltage
Driver Sink = +VIN, Driver Current = 100mA
Volts below +VIN
1.5
V
3.0
V
UVLO Sink Leakage
+VIN = C/S(+) = C/S(-) = 2.5V, Driver Sink = 15V, Driver
Source = 0V, TA = 25°C
Compensation/Shutdown = 0V; ISOURCE = 100µA,
25
µA
Maximum Reverse Source Voltage
+VIN = 3V
1.6
V
Thermal Shutdown
160
°C
Note 3: On the UCx833 this voltage is defined as the regulating level at the error amplifier inverting input, with the error amplifier
driving VSOURCE to 2V.
Note 4: These parameters are first-order supply-independent, however both may vary with supply for +VIN less than about 4V. This
supply variation will cause a slight change in the timer period and duty cycle, although a high off-time/on-time ratio will be maintained.
Note 5: With recommended RT value of 200k, TOFF ≈ RT CT * ln(Vu/Vl) ±10%.
Note 6: The internal current limiting voltage has a temperature dependence of approximately -2.0mV/°C, or -2800ppm/°C. The internal 2.4 Ω sense resistor has a temperature dependance of approximately +1500ppm/°C.
APPLICATION AND OPERATION INFORMATION
NPN Pass (Local 100mA Regulator) (UCx833)
UDG-92041-1
4
APPLICATION AND OPERATION INFORMATION (cont.)
UC1832/3
UC2832/3
UC3832/3
PNP Pass (Low Drop-Out Regulator) (UCx833)
UDG-92042-1
NPN Pass (Medium Power, Low Drop-Out Regulator) (UCx832)
UDG-92043-1
Estimating Maximum Load Capacitance
For any power supply, the rate at which the total output
Current Sense Amplifier Offset Voltage
and
K=
capacitance can be charged depends on the maximum
100mA
output current available and on the nature of the load. For
≈1.35 for UCx833, and is variable from 1.35 to 3.05
a constant-current current-limited power supply, the outwith VADJ for the UCx832.
put will come up if the load asks for less than the maxiFor a worst-case constant-current load of value just less
mum available short-circuit limit current.
than ITH, CMAX can be estimated from:
To guarantee recovery of a duty-ratio current-limited
TON
CMAX = ((K−1)ITH) (
),
power supply from a short-circuited load condition, there
VOUT
is a maximum total output capacitance which can be
where VOUT is the nominal regulator output voltage.
charged for a given unit ON time. The design value of ON
time can be adjusted by changing the timing capacitor. For a resistive load of value RL, the value of CMAX can be
estimated from:
Nominally, TON = 0.693 x 10k x CT.
TON
1
CMAX =
•
.
Typically, the IC regulates output current to a maximum of
RL
VOUT
In [(1−
) −1]
IMAX = K x ITH, where ITH is the timer trip-point current,
K • ITH • RL
5
UC1832/3
UC2832/3
UC3832/3
APPLICATION AND OPERATION INFORMATION (cont.)
Current Sense Amplifier Offset Voltage vs VADJ
UCx832/33 Timer Function
UCx832/33 Current Sense Input Configuration
Load current, timing capacitor voltage, and output voltage of
the regulator under fault conditions.
6
APPLICATION AND OPERATION INFORMATION (cont.)
UNITRODE CORPORATION
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 • FAX (603) 424-3460
7
UC1832/3
UC2832/3
UC3832/3
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