DATA SHEET
LND494
Pulse-Width-Modulation Control Circuits
GENERAL DESCRIPTION
FEATURES
The LND494 incorporate on a single monolithic
chip all the functions required in the construction
of a pulse-width-modulation control circuit.
Designed primarily for power supply control,
these devices offer the systems engineer the
flexibility to tailor the power supply control
circuitry to his application. The LND494
contains an error amplifier, an on-chip
adjustable oscillator, a dead time control
comparator, pulse –steering control flip-flop, a 5volt, 5% precision regulator, and output-control
circuits. The error amplifier exhibits a commonmode voltage range from –0.3 volts to Vcc-2
volts. The dead-time control compactor has a
fixed offset that provides approximately 5% dead
time when externally altered. The on-chip
oscillator may be by passed by terminating RT
(pin 6) to the reference output and providing a
sawtooth input to CT (pin 5), or it may be used to
drive the common circuits in synchronous
multiple-rail power supplies. The uncommitted
NON INV INPUT
output transistors provide either common-emitter
or emitter-follower output capability. Each
INV INPUT
device provides for push-pull or single-ended
output operation,
which may be selected through
`
the output-control function. The architecture of
FEEDBACK
these devices prohibits the possibility of either
output being pulsed twice during push-pull
DEAD-TIME CONTROL
operation.
•
•
•
•
•
•
Complete PWM Circuitry Power Control
Uncommitted Outputs for 200mA Sink
or source current
Output Control Selects Single-Ended or
Push-Pull operation
Internal Circuitry Prohibits Double
Pulse at Either Output
Variable Dead-Time Provides a stable
5-V Reference Supply, 5%
Circuit Architecture Allows Easy
Synchronization
LND494
(Top View)
1
16
NON INV INPUT
15
INV INPUT
3
14
REF OUT
4
13
OUTPUT CONTROL
CT
5
12
Vcc
RT
6
11
C2
GND
7
10
E2
C1
8
9
E1
2
Error
Amp1
Error
Amp2
• Linear Dmensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND494
ABSOLUTE MAXIMUM RATINGS
Rating
Supply voltage, Vcc
Amplifier input voltage
Collector output voltage
Collector output current
Operating free-air temperature
range
Storage temperature range
Lead temperature 1,6 mm from
case for 10 seconds
Value
41
Vcc+0.3
41
250
Unit
V
mA
0 to 70
-65 to 150
ºC
260
RECOMMENDED OPERATING CONDITIONS
Value
Parameter
Unit
Supply voltage, Vcc
Amplifier input voltage, Vi
Collector output voltage,Vo
Collector output current(each
transistor)
Current into feedback terminal
Timing capacitor,CT
Timing resistor, RT
Oscillator Frequency
Operating free-air temperature,
TA
MIN
7
-0.3
MAX
40
Vcc-2
40
V
200
mA
0.47
1.8
1
0.3
10000
500
300
nF
kΩ
kHz
0
70
ºC
FUNCTIONAL BLOCK DIAGRAM
OUTPUT CONTROL
RT
OSCILLATOR
CT
C1
DEAD TIME CONTROL
COMPARATOR
Q1
0.1V
DEAD
TIME
CONTROL
E1
C1
C2
NON INVERTING
INPUT
INVERTING
INPUT
NON INVERTING
INPUT
INVERTING
INPUT
Q2
ERROR
AMPLIFIER
+
PWM
COMPARATOR
1
PULSE STEERING
FLIP - FLOP
E2
-
2
-
VCC
ERROR
AMPLIFIER
+
REFERENCE
FEEDBACK
VREF
GND
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND494
PARAMETER MEASUREMENT INFORMATION
Vc c = 15V
V
{
150
2W
DEAD TIME
TEST
INPUTS
150
2W
CC
C1
E1
OUTPUT 1
C2
E2
OUTPUT 2
FEEDBACK
12k
RT
.01uF
CT
+1
-1
+2
-2
}
ERROR
50k
OUTPUT
CONTROL
REF
OUT
GND
TEST CIRCUIT
Vcc
Voltage At
C1
0
Vcc
Voltage At
C2
0
Voltage At
CT
Threshold Voltage
Dead-Time
Control
Input
+
AMPLIFIER
UNDER TEST
FEEDBACK
TERMINAL
VI
-
0V
Threshold Voltage
+
Feedback
0.7V
MAX
Duty Circle
0%
VREF
OTHER
AMPLIFIER
-
0%
VOLTAGE WAVEFORMS
Figure 1: Operational Test Circuit and Waveforms
Figure 2: Amplifier Characteristics
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND494
15V
15V
68
2W
90%
tf
OUTPUT
tr
90%
OUTPUT
90%
68
2W
C L = 15pF
C = 15pF
L
10%
tr
10%
TEST CIRCUIT
90%
10%
tf
10%
OUTPUT VOLTAGE WAVEFORM
Figure 3: Common-Emitter Configuration
OUTPUT VOLTAGE WAVEFORM
TEST CIRCUIT
Figure 4: Emitter-Follower Configuration
ELECTRICAL CHARACTERISTICS
Electrical characteristics over recommended operating free-air temperature range Vcc=15V, f=10kHz(unless otherwise
noted)
Reference Section
Value
Parameter
Test conditions*
Output voltage(Vref)
Input regulation
Output regulation
Output voltage change
with temperature
Short-circuit output
current***
Io=1mA
Vcc=7V to 40V
Io=1mA to 10mA
MIN
TYP**
MAX
4.75
5
2
1
5.25
25
15
∆TA = MIN to MAX
0.2
1
Vref=0
35
Unit
V
mV
%
mA
Oscillator Section (See Figure 1)
Value
Parameter
Test conditions*
Unit
MIN
Frequency
Standard deviation of
frequency ****
Frequency change with
voltage
Frequency change with
temperature*****
CT=0.01µF,RT =12kΩ
All values of VCC, CT, RT
and TA constant
Vcc=7V to 40V, TA=25ºC
CT =0.01µF, RT
=12kΩ,∆TA=MIN TO
MAX
TYP
MAX
10
kHz
10
0.1
%
1
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND494
Amplifier Section (See Figure 2)
Value
Parameter
Test conditions
Input Offset Voltage
Input Offset Current
Input Bias Current
Vo=(pin 3)=2.5V
Vo=(pin 3)= 2.5V
Vo=(pin 3)=2.5V
Common Mode Input
Voltage Range
Vcc=7V to 40V
Open Loop Voltage
Amplification
Unity Gain Bandwidth
Common- Mode
Rejection Ratio
Output Sink Current
Output Source Current
Vo=3V,RL=2kΩ
Vo=0.5 to 3.5V
Vo=0.5 to 3.5V, RL=2kΩ
Vo=40V,TA = 25º C
VID= -15Mv TO –5v
V(PIN3) =0.7v
VID= -15mV TO –5V
V(PIN3) =3.5v
MIN
TYP
MAX
2
25
0.2
10
250
1
Unit
mV
nA
µA
-0.3
to
Vcc-2
V
70
95
DB
800
kHZ
65
80
dB
0.3
0.7
mA
-2
mA
*For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating
conditions.
** All typical values except for parameter changes with temperature are at TA =25º C
***Duration of the short-circuit should not exceed one second.
****Standard deviation is a measure of the statistical distribution about the mean as derived from the formula.
1/2
σ=
[∑
N
( xn - x )2
N-1
n=1
]
******Temperature coefficient of timing capacitor and timing resistor not taken into account
Output Section
Parameter
Collector off-state
current
Emitter off-state current
Collector-emitter
saturation Voltage
Common-Emitter
Emitter-Follower
Output control input
current
Test conditions
Vce=40V Vcc =40 V
MIN
Value
TYP*
MAX
2
100
µA
-100
%
Vce=Vcc=40V Ve=0
Unit
V
Ve=0,Ic=200mA
Vc=15V, Ie=-200mA
VI=Vref
1.1
1.5
1.3
2.5
3.5
mA
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •
LND494
Dead-Time Control Section (See figure 1)
Parameter
Test conditions
Input Bias current (pin4)
Maximum Duty
Cycle,Each output
VI=0 to 5.25V
VI(pin 4)=0,CT =0.1µF,
RT =12KΩ
Zero duty cycle
Maximum Duty Cycle
Input Threshold Voltage
(pin4)
MIN
Value
TYP*
-2
Unit
MAX
-10
µA
45
3
%
3.3
V
0
PWM comparator section (see figure 1)
Parameter
Test Conditions
Input threshold voltage
(pin 3)
Input sink current (pin 3)
Zero duty cycle
V(pin3)= 0.7V
MIN
0.3
Value
TYP*
4
Unit
MAX
4.5
V
0.7
mA
Total Device
Parameter
Test Conditions
Standby supply
current
Average supply
current
Pin 6 at Vref, all other
Vcc=15V
inputs and outputs open Vcc=40V
VI ( pin 4) =2V, See figure 1
MIN
Value
TYP
6
9
7.5
MAX
10
15
Unit
mA
Switching characteristics, Ta=25ºC
PARAMETER
TEST CONDITIONS
Output voltage rise time
Common-emitter configuration
See figure 3
Output voltage fall time
Output voltage rise time
Emitter-follower configuration
See Figure 4
Output voltage fall time
*All typical values except for temperature coefficient at TA= 25ºC
MIN
VALUE
TYP*
100
25
100
40
MAX
200
100
200
100
UNIT
nS
• Linear Dimensions, Inc. • 445 East Ohio Street, Chicago IL 60611 USA • tel 312.321.1810 • fax 312.321.1830 • www.lineardimensions.com •