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DATA SHEET
LND494
Pulse-Width-Modulation Control Circuits
GENERAL DESCRIPTION
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.
CT RT GND C1
FEATURES
* * * * * *
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 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 NON INV INPUT INV INPUT REF OUT OUTPUT CONTROL Vcc C2 E2 E1
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 0 to 70 -65 to 150 260 C Unit V mA
RECOMMENDED OPERATING CONDITIONS
Value Parameter 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 40 200 0.47 1.8 1 0 0.3 10000 500 300 70 Unit
V
mA nF k kHz C
FUNCTIONAL BLOCK DIAGRAM
OUTPUT CONTROL
RT CT
OSCILLATOR
DEAD TIME CONTROL COMPARATOR
C1 Q1 C1 E1 C2
DEAD TIME CONTROL
0.1V
NON INVERTING INPUT INVERTING INPUT NON INVERTING INPUT INVERTING INPUT
Q2
+ 1 -
ERROR AMPLIFIER
PWM COMPARATOR
PULSE STEERING FLIP - FLOP
E2
+ 2 -
ERROR AMPLIFIER FEEDBACK
VCC REFERENCE 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
V c = 15V c
V TEST INPUTS
150 2W CC C1 E1 C2 E2
150 2W OUTPUT 1
{
12k
DEAD TIME FEEDBACK
OUTPUT 2
RT .01uF CT +1 -1 +2 -2 50k OUTPUT CONTROL GND
}
ERROR
REF OUT
TEST CIRCUIT
Voltage At C1
Vcc 0 Vcc
Voltage At C2
0
Voltage At CT
Threshold Voltage Dead-Time Control Input
+ VI
AMPLIFIER UNDER TEST FEEDBACK TERMINAL
0V
Threshold Voltage
-
Feedback
+
OTHER AMPLIFIER
0.7V
Duty Circle
MAX
0%
VREF
-
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 68 2W
15V 90% 90%
tf
OUTPUT C = 15pF L 90%
tr
90% C L = 15pF OUTPUT 68 2W 10% 10%
tr
10% 10%
tf
TEST CIRCUIT
OUTPUT VOLTAGE WAVEFORM
TEST CIRCUIT
OUTPUT VOLTAGE WAVEFORM
Figure 3: Common-Emitter Configuration
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 Output voltage(Vref) Input regulation Output regulation Output voltage change with temperature Short-circuit output current*** Test conditions* Io=1mA Vcc=7V to 40V Io=1mA to 10mA TA = MIN to MAX Vref=0 MIN 4.75 TYP** 5 2 1 0.2 35 MAX 5.25 25 15 1 Unit V mV % mA
Oscillator Section (See Figure 1) Value Parameter Frequency Standard deviation of frequency **** Frequency change with voltage Frequency change with temperature***** Test conditions* MIN CT=0.01F,RT =12k All values of VCC, CT, RT and TA constant Vcc=7V to 40V, TA=25C CT =0.01F, RT =12k,TA=MIN TO MAX TYP 10 10 0.1 1 % MAX kHz Unit
* 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 Input Offset Voltage Input Offset Current Input Bias Current Common Mode Input Voltage Range Open Loop Voltage Amplification Unity Gain Bandwidth Common- Mode Rejection Ratio Output Sink Current Output Source Current Test conditions Vo=(pin 3)=2.5V Vo=(pin 3)= 2.5V Vo=(pin 3)=2.5V Vcc=7V to 40V Vo=3V,RL=2k Vo=0.5 to 3.5V Vo=0.5 to 3.5V, RL=2k Vo=40V,TA = 25 C VID= -15Mv TO -5v V(PIN3) =0.7v VID= -15mV TO -5V V(PIN3) =3.5v -0.3 to Vcc-2 70 95 800 65 0.3 -2 80 0.7 MIN TYP 2 25 0.2 MAX 10 250 1 Unit mV nA A V DB kHZ dB mA 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 =25 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 =
[
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 Vce=Vcc=40V Ve=0 Value TYP* 2 Unit A % V Ve=0,Ic=200mA Vc=15V, Ie=-200mA VI=Vref 1.1 1.5 1.3 2.5 3.5 mA
MIN
MAX 100 -100
* 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 Input Bias current (pin4) Maximum Duty Cycle,Each output Input Threshold Voltage (pin4) Test conditions VI=0 to 5.25V VI(pin 4)=0,CT =0.1F, RT =12K Zero duty cycle Maximum Duty Cycle Value TYP* -2 45 3 0 3.3 Unit A % V
MIN
MAX -10
PWM comparator section (see figure 1) Parameter Input threshold voltage (pin 3) Input sink current (pin 3) Total Device Parameter Standby supply current Average supply current Test Conditions Pin 6 at Vref, all other Vcc=15V inputs and outputs open Vcc=40V VI ( pin 4) =2V, See figure 1 Value TYP 6 9 7.5 Unit mA Test Conditions Zero duty cycle V(pin3)= 0.7V 0.3 Value TYP* 4 0.7 Unit MAX 4.5 V mA
MIN
MIN
MAX 10 15
Switching characteristics, Ta=25C PARAMETER TEST CONDITIONS VALUE TYP* 100 25 100 40 UNIT
MIN
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= 25C
MAX 200 100 200 100
nS
* Linear Dimensions, Inc. * 445 East Ohio Street, Chicago IL 60611 USA * tel 312.321.1810 * fax 312.321.1830 * www.lineardimensions.com *

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