TI UC3715N

UC1714/5
UC2714/5
UC3714/5
Complementary Switch FET Drivers
FEATURES
DESCRIPTION
• Single Input (PWM and TTL
Compatible)
• Time Delays Between Power and
Auxiliary Outputs Independently
Programmable from 50ns to 500ns
These two families of high speed drivers are designed to provide drive
waveforms for complementary switches. Complementary switch configurations are commonly used in synchronous rectification circuits and active
clamp/reset circuits, which can provide zero voltage switching. In order to
facilitate the soft switching transitions, independently programmable delays between the two output waveforms are provided on these drivers.
The delay pins also have true zero voltage sensing capability which allows
immediate activation of the corresponding switch when zero voltage is applied. These devices require a PWM-type input to operate and can be interfaced with commonly available PWM controllers.
• Time Delay or True Zero-Voltage
Operation Independently Configurable
for Each Output
In the UC1714 series, the AUX output is inverted to allow driving a
p-channel MOSFET. In the UC1715 series, the two outputs are configured
in a true complementary fashion.
• High Current Power FET Driver, 1.0A
Source/2A Sink
• Auxiliary Output FET Driver, 0.5A
Source/1A Sink
• Switching Frequency to 1MHz
• Typical 50ns Propagation Delays
• ENBL Pin Activates 220µA Sleep
Mode
• Power Output is Active Low in Sleep
Mode
• Synchronous Rectifier Driver
BLOCK DIAGRAM
2
PWR
50ns –500ns
4
AUX
TIMER
S
Q
1
VCC
3
GND
50ns –500ns
INPUT
6
TIMER
S
Q
T1
7
R
T2
UC1714
ONLY
VREF
5
R
VREF
VCC
5V
BIAS
ENBL 3V
GND
LOGIC
GATES
TIMER
REF
1.4V
ENBL
8
ENABLE
Note: Pin numbers refer to J, N and D packages.
02/99
UDG-99028
UC1714/5
UC2714/5
UC3714/5
ABSOLUTE MAXIMUM RATINGS
Input Voltage Range (INPUT, ENBL) . . . . . . . . . . −0.3V to 20V
Storage Temperature Range . . . . . . . . . . . . . . −65°C to 150°C
Operating Junction Temperature (Note 1) . . . . . . . . . . . . 150°C
Lead Temperature (Soldering 10 seconds) . . . . . . . . . . . 300°C
Supply Voltage VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20V
Power Driver IOH
continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −200mA
peak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −1A
Power Driver IOL
continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400mA
peak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2A
Auxiliary Driver IOH
continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −100mA
peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . −500mA
Auxiliary Driver IOL
continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200mA
peak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A
Note 1: Unless otherwise indicated, voltages are referenced to
ground and currents are positive into, negative out of, the specified terminals.
Note 2: Consult Packaging Section of databook for thermal limitations and specifications of packages.
CONNECTION DIAGRAMS
DIL-8, SOIC-8 (Top View)
J or N, D Packages
SOIC-16 (Top View)
DP Package
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, VCC = 15V, ENBL ≥ 2V, RT1 = 100kΩ from T1 to GND,
RT2 = 100kΩ from T2 to GND, and −55°C < TA < 125°C for the UC1714/5, −40°C < TA < 85°C for the UC2714/5, and 0°C < TA <
70°C for the UC3714/5, TA = TJ.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX UNITS
Overall
20
V
ICC, nominal
ENBL = 2.0V
7
18
24
mA
ICC, sleep mode
ENBL = 0.8V
200
300
µA
VCC
Power Driver (PWR)
Pre Turn-on PWR Output, Low
VCC = 0V, IOUT = 10mA, ENBL  0.8V
0.3
1.6
V
PWR Output Low, Sat. (VPWR)
INPUT = 0.8V, IOUT = 40mA
0.3
0.8
V
INPUT = 0.8V, IOUT = 400mA
2.1
2.8
V
PWR Output High, Sat. (VCC − VPWR)
INPUT = 2.0V, IOUT = −20mA
2.1
3
V
INPUT = 2.0V, IOUT = −200mA
2.3
3
V
Rise Time
CL = 2200pF
30
60
ns
Fall Time
CL = 2200pF
25
60
ns
T1 Delay, AUX to PWR
INPUT rising edge, RT1 = 10kΩ (Note 4)
20
35
80
ns
T1 Delay, AUX to PWR
INPUT rising edge, RT1 = 100kΩ (Note 4)
350
500
700
ns
PWR Prop Delay
INPUT falling edge, 50% (Note 3)
35
100
ns
2
UC1714/5
UC2714/5
UC3714/5
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, VCC = 15V, ENBL ≥ 2V, RT1 = 100kΩ from T1 to GND,
RT2 = 100kΩ from T2 to GND, and −55°C < TA < 125°C for the UC1714/5, −40°C < TA < 85°C for the UC2714/5, and 0°C < TA <
70°C for the UC3714/5, TA = TJ.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX UNITS
Auxiliary Driver (AUX)
AUX Output Low, Sat
(VAUX)
AUX Output High, Sat (VCC – VAUX)
VIN = 2.0V, IOUT = 20mA
0.3
0.8
V
VIN = 2.0V, IOUT = 200mA
1.8
2.6
V
VIN = 0.8V, IOUT = -10mA
2.1
3.0
V
VIN = 0.8V, IOUT = -100mA
2.3
3.0
V
Rise Time
CL = 1000pF
45
60
ns
Fall Time
CL = 1000pF
30
60
ns
T2 Delay, PWR to AUX
INPUT falling edge, RT2 = 10kΩ (Note 4)
20
50
80
ns
T2 Delay, PWR to AUX
INPUT falling edge, RT2 = 100kΩ (Note 4)
250
350
550
ns
AUX Prop Delay
INPUT rising edge, 50% (Note 3)
35
80
ns
Enable (ENBL)
Input Threshold
1.2
2.0
V
Input Current, IIH
ENBL = 15V
0.8
1
10
µA
Input Current, IIL
ENBL = 0V
−1
−10
µA
−1.6
−2
mA
3
3.3
V
40
70
ns
−1.2
−2
mA
3
3.3
V
50
100
ns
T1
Current Limit
T1 = 0V
Nominal Voltage at T1
Minimum T1 Delay
2.7
T1 = 2.5V, (Note 4)
T2
Current Limit
T2 = 0V
Nominal Voltage at T2
Minumum T2 Delay
2.7
T2 = 2.5V, (Note 4)
Input (INPUT)
Input Threshold
1.4
2.0
V
Input Current, IIH
INPUT = 15V
0.8
1
10
µA
Input Current, IIL
INPUT = 0V
−5
−20
µA
Note 3: Propagation delay times are measured from the 50% point of the input signal to the 10% point of the output signal’s transition with no load on outputs.
Note 4: T1 delay is defined from the 50% point of the transition edge of AUX to the 10% of the rising edge of PWR. T2 delay is defined from the 90% of the falling edge of PWR to the 50% point of the transition edge of AUX.
PIN DESCRIPTIONS
AUX: The AUX switches immediately at INPUT’s rising
edge but waits through the T2 delay after INPUT’s falling
edge before switching. AUX is capable of sourcing 0.5A
and sinking 1.0A of drive current. See the Time Relationships diagram below for the difference between the
UC1714 and UC1715 for INPUT, MAIN, and AUX. During
sleep mode, AUX is inactive with a high impedance.
The ENBL input will place the device into sleep mode
when it is a logical low. The current into VCC during the
sleep mode is typically 220µA.
GND: This is the reference pin for all input voltages and
the return point for all device currents. It carries the full
peak sinking current from the outputs. Any tendency for
the outputs to ring below GND voltage must be damped
or clamped such that GND remains the most negative
potential.
ENBL: The ENBL input switches at TTL logic levels (approximately 1.2V), and its input range is from 0V to 20V.
3
UC1714/5
UC2714/5
UC3714/5
PIN DESCRIPTIONS (cont.)
INPUT: The input switches at TTL logic levels (approximately 1.4V) but the allowable range is from 0V to 20V,
allowing direct connection to most common IC PWM controller outputs. The rising edge immediately switches the
AUX output, and initiates a timing delay, T1, before
switching on the PWR output. Similarly, the INPUT falling
edge immediately turns off the PWR output and initiates
a timing delay, T2, before switching the AUX output.
T2: This pin functions in the same way as T1 but controls
the time delay between PWR turn-off and activation of
the AUX switch.
T1, T2: The resistor on each of these pins sets the
charging current on internal timing capacitors to provide
independent time control. The nominal voltage level at
each pin is 3V and the current is internally limited to
1mA. The total delay from INPUT to each output includes
a propagation delay in addition to the programmable
timer but since the propagation delays are approximately
equal, the relative time delay between the two outputs
can be assumed to be solely a function of the programmed delays. The relationship of the time delay vs.
RT is shown in the Typical Characteristics curves.
It should be noted that if the input signal comes from a
controller with FET drive capability, this signal provides
another option. INPUT and PWR provide a delay only at
the leading edge while INPUT and AUX provide the delay
at the trailing edge.
PWR: The PWR output waits for the T1 delay after the
INPUT’s rising edge before switching on, but switches off
immediately at INPUT’s falling edge (neglecting propagation delays). This output is capable of sourcing 1A and
sinking 2A of peak gate drive current. PWR output includes a passive, self-biased circuit which holds this pin
active low, when ENBL ≥ 0.8V regardless of VCC’s voltage.
Either or both pins can alternatively be used for voltage
sensing in lieu of delay programming. This is done by
pulling the timer pins below their nominal voltage level
which immediately activates the timer output.
VCC: The VCC input range is from 7V to 20V. This pin
should be bypassed with a capacitor to GND consistent
with peak load current demands.
T1: A resistor to ground programs the time delay between AUX switch turn-off and PWR turn-on.
TYPICAL CHARACTERISTICS
INPUT
PROPAGATION
DELAYS
PWR OUTPUT
T1 vs RT1
T2 vs RT2
500
400
T2 DELAY
DELAY (ns)
T1 DELAY
UC1714 AUX OUTPUT
300
200
100
0
UC1715 AUX OUTPUT
0
10
20
30
40
UDG-99027
Time relationships. (Notes 3, 4)
T1 Delay, T2 Delay vs. RT
4
50
60
RT (kW)
70
80
90
100
UC1714/5
UC2714/5
UC3714/5
TYPICAL CHARACTERISTICS (cont.)
21
18
17
19
Icc (mA)
Icc (mA)
20
18
16
17
16
15
0 100 200 300 400 500 600 700 800 900 1000
0
10
20
30
40
ICC vs Switching Frequency with No Load and 50%
Duty Cycle RT1 = RT2 = 50k
70
80
90
100
75
100
600
RT1 = 100k
500
Deadband Delay (ns)
500
Deadband Delay (ns)
60
ICC vs RT with Opposite RT = 50k
600
400
300
RT1 = 50k
200
100
0
-75
50
RT (kΩ)
Switching Frequency (kHz)
400
RT2 = 100k
300
RT2 = 50k
200
100
RT1 = 10k
RT1 < 6k
-50
-25
0
25
50
Temperature (°C)
75
100
0
-75
125
RT2 = 10k
RT2 < 6k
-50
-25
0
25
50
125
Temperature (°C)
T1 Deadband vs. Temperature AUX to PWR
T2 Deadband vs. Temperature PWR to AUX
TYPICAL APPLICATIONS
UDG-94011
Figure 1. Typical application with timed delays.
UDG-94012
Figure 2. Using the timer input for
zero-voltage sensing.
5
UC1714/5
UC2714/5
UC3714/5
TYPICAL APPLICATIONS (cont.)
UDG-94013
Figure 3. Self-actuated sleep mode with the absence of an input PWM signal. Wake up occurs with the first
pulse while turn-off is determined by the (RTO CTO) time constant.
UDG-94015-2
Figure 4. Using the UC1715 as a complementary synchronous rectifier switch driver with n-channel FETs
UDG-94014-1
Figure 5. Synchronous rectifier application with a charge pump to drive the high-side n-channel buck switch.
VIN is limited to 10V as VCC will rise to approximately 2VIN.
6
UC1714/5
UC2714/5
UC3714/5
TYPICAL APPLICATIONS (cont.)
UDG-94016-1
Figure 6. Typical forward converter topology with active reset provided by the UC1714 driving an N-channel
switch (Q1) and a P-channel auxilliary switch (Q2).
UDG-94017-1
Figure 7. Using an N-channel active reset switch with a floating drive command.
Vicor Corporation has claimed that the use of active reset in a forward converter topology is covered under its U.S.
Patent 4,441,146. Unitrode is not suggesting or encouraging persons to infringe or use Vicor’s patented technology absent a
license from Vicor.
UNITRODE CORPORATION
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 • FAX (603) 424-3460
7
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