NTE NTE1721

NTE1721 & NTE1723
Integrated Circuit
Pulse Width Modulator (PWM) Regulator
Description:
The NTE1721 and NTE1723 are pulse width modulator control–circuits designed to offer improved
performance and lowered external parts count when implemented for controlling all types of switching
power supplies. The no–chip +5.1V reference is trimmed to ±1% and the input common–mode range
of the errror amplifier includes the reference voltage, thus eliminating the need for external divider
resistors. A sync input to the oscillator enables multiple units to be slaved or a single unit to be synchronized to an external system clock. A wide range of dead time can be programmed by a single
resistor connected between the CT and the Discharge pins. These devices also feature a built–in
soft–start circuitry, requiring only an external timing capacitor. A shutdown pin controls both the soft–
start circuitry and the output stages, provided instantaneous turn–off through the PWM latch with
pulsed shutdown, as well as soft–start recycle with longer shutdown commands. The under voltage
lockout inhibits the outputs and the changing of the soft–start capacitor when VCC is below nominal.
The output stages are totem–pole design capable of sinking and sourcing in excess of 200mA. The
output stages of the NTE1721 features NOR logic resulting in a low output for an off state while the
NTE1723 utilizes OR logic which gives a high output when off.
Features:
D 8V to 35V Operation
D +5.1V ±1% Trimmed Reference
D 100Hz to 400kHz Oscillator Range
D Separate Oscillator Sync Pin
D Adjustable Dead Time Control
D
D
D
D
Input Undervoltage Lockout
Latching PWM to Prevent Multiple Pulses
Pulse–by–Pulse Shutdown
Dual Source/Sink Outputs: ±400mA Peak
Absolute Maximum Ratings: (Note 1)
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V
Collector Supply Voltage, VC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V
Logic Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to +5.5V
Analog Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to VCC
Output Current, Source or Sink, IO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±500mA
Reference Output Current, Iref . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA
Oscillator Charging Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA
Power Dissipation (TA = +25°C), PD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW
Derate Above 50°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10mW/°C
Power Dissipation (TC = +25°C), PD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000mW
Derate Above 25°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16mW/°C
Operating Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C
Storage Temperature Range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –55° to +125°C
Thermal Resistance, Junction–to–Ambient, RthJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100°C/W
Thermal Resistance, Junction–to–Case, RthJC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60°C/W
Lead Temperature (During Soldering, 10sec), TL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +300°C
Note 1 Values beyond which damage may occur
Recommended Operating Conditions:
Parameter
Symbol
Min
Typ
Max
Unit
Supply Voltage
VCC
8.0
–
35.0
V
Collector Supply Voltage
VC
4.5
–
35.0
V
Output Sink/Source Current
Steady State
IO
0
–
±100
mA
0
–
±400
mA
Peak
Reference Load Current
Iref
0
–
20
mA
Oscillator Frequency Range
fosc
0.1
–
400
kHz
Oscillator Timing Resistor
RT
2.0
–
150
kΩ
Oscillator Timing Capacitor
CT
0.001
–
0.2
µF
Deadtime Resistor Range
RD
0.5
–
–
Ω
Operating Ambient Temperature Range
TA
0
–
70
°C
Electrical Characteristics: (VCC = +20V, TA = 0° to +70°C unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
5.0
5.1
5.2
V
Reference Section
Reference Output Voltage
Vref
TJ = +25°C
Line Regulation
Regline
+8V ≤ VCC ≤ +35V
–
10
20
mV
Load Regulation
Regload
0mA ≤ IL ≤ 20mA
–
20
50
mV
Temperature Stability
∆Vref/∆T
–
20
–
mV
∆Vref
4.95
–
5.25
V
Total Output Variation (Includes Line
and Load Regulation over
Temperature
Short Circuit Current
ISC
Vref = 0V, TJ = +25°C
–
80
100
mA
Output Noise Voltage
Vn
10Hz ≤ f ≤ 10kHz, TJ = +25°C
–
40
200
µVrms
Long Term Stability
S
TJ = +25°C, Note 2
–
20
50
mV/kHr
Oscillator Section (Tested at fosc = 40kHz, RT = 3.6kΩ, CT = 0.001µF, RD = 0Ω unless otherwise specified)
Initial Accuracy
Frequency Stability with Voltage
Frequency Stability with Temperature
fosc/VCC
TJ = +25°C
–
±2
±6
%
+8V ≤ VCC ≤ +35V
–
±1
±2
%
–
±3
–
%
–
50
–
Hz
fosc/T
Minimum Frequency
fmin
RT = 150kΩ, CT = 0.2µF
Maximum Frequency
fmax
RT = 2kΩ, CT = 1.0nF
400
–
–
kHz
IRT = 2mA
1.7
2.0
2.2
mA
3.0
3.5
–
V
0.3
0.5
1.0
µs
1.2
2.0
2.8
V
–
1.0
2.5
mA
Current Mirror
Clock Amplitude
Clock Width
TJ = +25°C
Sync Threshold
Sync Input Current
Sync Voltage = +3.5V
Error Amplifier Section (VCM = +5.1V)
Input Offset Voltage
VIO
–
2.0
10.0
mV
Input Bias Current
IIB
–
1.0
10.0
µA
Note 2. Since long term stability cannot be measured on each device before shipment, this specification is an engineering estimate of average stability from lot to lot.
Electrical Characteristics (Cont’d): (VCC = +20V, TA = 0° to +70°C unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
60
75
–
dB
Error Amplifier Section (Cont’d) (VCM = +5.1V)
RL ≤ 10MΩ
DC Open Loop Gain
AVOL
Low Level Output Voltage
VOL
–
0.2
0.5
V
High Level Output Voltage
VOH
3.8
5.6
–
V
Common Mode Rejection Ratio
CMRR
+1.5V≤ VCM ≤ +5.2V
60
75
–
dB
Power Supply Rejection Ratio
PSRR
+8V ≤ VCC ≤ +35V
50
60
–
dB
PWM Comparator Section
Minimum Duty Cycle
DCmin
–
–
0
%
Maximum Duty Cycle
DCmax
45
49
–
%
0.6
0.9
–
V
–
3.3
3.6
V
–
0.05
1.0
µA
Input Threshold, Zero Duty Cycle
VTH
Input Threshold, Maximum Duty Cycle
Input Bias Current
fosc = 40kHz, RT = 3.6kΩ,
CT = 0.01µF, RD = 0Ω
Ω
IIB
Soft–Start Section
Soft–Start Current
Vshutdown = 0V
25
50
80
µA
Soft–Start Voltage
Vshutdown = 2.0V
–
0.4
0.6
V
Shutdown Input Current
Vshutdown = 2.5V
–
0.4
1.0
mA
Isink = 20mA
–
0.2
0.4
V
Isink = 100mA
–
1.0
2.0
V
Isink = 20mA
18
19
–
V
Isink = 100mA
17
18
–
V
VUL
V8 and V9 = High
6.0
7.0
8.0
V
IC(leak)
VC = +35V, Note 3
–
–
200
µA
Output Drivers (Each Output, VCC = +20V)
Output Low Level
Output High Level
Under Voltage Lockout
Collector Leakage
VOL
VOH
Rise Time
tr
CL = 1.0nF, TJ = +25°C
–
100
600
ns
Fall Time
tf
CL = 1.0nF, TJ = +25°C
–
50
300
ns
Shutdown Delay
tds
VDS = +3V, CS = 0, TJ = +25°C
–
0.2
0.5
µs
Supply Current
ICC
VCC = +35V
–
14
20
mA
Note 3.Applies to NTE1721 Only, due to polarity of output pulses.
Application Information (Shutdown Options):
Since both the compensation and soft–start terminals (Pin9 and Pin8) have current source pull–ups,
either can readily accept a pull–down signal which only has to sink a maximum of 100µA to turn off
the outputs. This is subject to the added requirement of discharging whatever external capacitance
may be attached to these pins.
An alternate approach is the use of the shutdown circuitry of Pin10 which has been improved to enhance the available shutdown options. Activating this circuit by applying a positive signal on Pin10
performs two functions: the PWM latch is immediately set providing the fastest turn–off signal to the
outputs; and a 150µA current sink begins to discharge the external soft–start capacitor. If the shutdown command is short, the PWM signal is terminated without significant discharge of the soft–start
capacitor, thus, allowing, for example, a convenient implementation of pulse–by–pulse current limiting. Holding Pin10 high for a longer duration, however, will ultimately discharge this external capacitor, recycling slow turn–on upon release.
Pin10 should not be left floating as noise pickup could conceivably interrupt normal operation.
Pin Connection Diagram
Invert Input 1
16 Vref
Non–Invert Input 2
15 VIN
Sync 3
14 Output B
13 VC
OSC Output 4
CT
5
12 GND
RT
6
11 Output A
Discharge 7
10 Shutdown
Soft–Start 8
9 Compensation
16
9
1
8
.870 (22.0) Max
.260 (6.6)
Max
.200 (5.08)
Max
.100 (2.54)
.700 (17.78)
.099 (2.5) Min