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Электронный компонент: TC38C43CPD

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4-93
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
BiCMOS CURRENT MODE PWM CONTROLLERS
UNDER VOLTAGE
SECTION
VREF
OSC
12
9
5
3
1
2R
ERROR AMP
LIMIT BUFFER
R
CLK
PWM COMPARATOR
2.5V
1.4V
UV GOOD
14
VREF
7
R /
T CT
VDD
11
OUTPUT
10
PIN NUMBERS FOR
14-PIN DIP
COMP
VFB
2.5V
SENSE
ANALOG
GND
VIN
CLK
0.4V
+
+
+
S
R
POWER
GROUND
8
Q
1.4V
+
TC38C43-7 10/21/96
FEATURES
s
Low Power BiCMOS Design
s
Tough CMOS
TM
Construction
s
Low Supply Current ............. 1.0mA Typ @ 100kHz
s
Wide Supply Voltage Operation .............. 8V to 15V
s
Latch-Up Immunity ................... 500mA on Outputs
s
Input Will Withstand Negative Inputs to 5 Volts
s
High Output Drive .................................... 0.7A Peak
(1.2A on 14-Pin and 16-Pin Versions)
s
2 kV ESD Protection
s
Current Mode Control
s
Fast Rise/Fall Time (Max) ........... 60nsec @ 1000pF
s
High Frequency Operation ..........................500kHz
s
Clock Ramp Reset Current ................. 2.5mA
10%
s
Low Propagation Delay Current Amp
to Output ............................................ 140nsec Typ.
s
Pin Compatible with UC3843
ORDERING INFORMATION
Part No.
Package
Temperature
TC18C43MJA
8-Pin CerDIP
55
C to +125
C
TC18C43MJD
14-Pin CerDIP
55
C to +125
C
TC28C43EOE
16-Pin SOIC (Wide)
40
C to +85
C
TC28C43EPA
8-Pin Plastic DIP
40
C to +85
C
TC28C43EPD
14-Pin Plastic DIP
40
C to +85
C
TC38C43COE
16-Pin SOIC (Wide)
0
C to +70
C
TC38C43CPA
8-Pin Plastic DIP
0
C to +70
C
TC38C43CPD
14-Pin Plastic DIP
0
C to +70
C
GENERAL DESCRIPTION
The TC38C43 is a current mode BiCMOS PWM control
IC. With a low 1.0 mA supply current along with high drive
current (0.7A peak) it provides a low cost solution for a PWM
that operates to 500 kHz and directly drives MOSFETs up to
HEX 3 size.
Performance of the oscillator and current sense ampli-
fier have been greatly improved over previous bipolar ver-
sions. Voltage and temperature stability have been im-
proved by a factor of 3. Noise immunity (PSRR) has also
been improved.
The TC38C43 is pin compatible with the earlier bipolar
version so that designers can easily update older designs.
Improvements have been added, though. For example,
clock ramp reset current is specified at 2.5mA (
10%) for
accurate dead time control. A few component values must
be changed (R
T
& C
T
) to use the TC38C43 in existing bipolar
designs.
The 14-pin DIP and 16-pin SOIC versions have sepa-
rate and internally isolated grounds, and are rated for higher
output current (1.2A). These separate grounds allow for
`bootstrap' operation of the PWM to further improve effi-
ciency.
FUNCTIONAL BLOCK DIAGRAM
1
2
3
4
8
7
6
5
VREF
CMPTR
OUTPUT
ISENSE
VIN
GND
RT/ CT
VFB
TC18CMJA
TC28CEPA
TC38CCPA
NC
NC
NC
OUTPUT
POWER
GND
GND
NC
VREF
VIN
RT/ CT
ISENSE
CMPTR
VDD
VFB
1
14
2
13
3
12
4
11
5
10
6
9
7
8
1
2
3
4
16
15
14
13
9
8
NC
NC
NC
NC
OUTPUT
POWER
GND
GND
NC
VREF
VIN
CMPTR
VDD
VFB
TC18CMJD
TC28CEPD
TC38CCPD
12
11
10
5
6
7
NC
RT/ CT
ISENSE
TC28CCOE
TC38CEOE
14-Pin Plastic DIP
16-Pin SOIC (Wide)
8-Pin Plastic DIP
PIN CONFIGURATIONS
TC18C43
TC28C43
TC38C43
4-94
TELCOM SEMICONDUCTOR, INC.
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage ............................................................ 18V
Maximum Chip Temperature ................................... 150
C
Storage Temperature ............................ 65
C to +150
C
Lead Temperature (Soldering, 10 sec) ................. +300
C
Package Thermal Resistance
CerDip R
J-A
................................................ 150
C/W
CerDip R
J-C
.................................................. 55
C/W
PDIP R
J-A
................................................... 125
C/W
PDIP R
J-C
..................................................... 45
C/W
SOIC R
J-A
................................................... 250
C/W
SOIC R
J-C
..................................................... 75
C/W
Operating Temperature
18C4x ...................................... 55C
T
A
+125
C
28C4x ........................................ 40C
T
A
+85
C
38C4x ............................................. 0C
T
A
+70
C
ELECTRICAL CHARACTERISTICS
unless otherwise stated, these specifications apply over specific
temperature range. V
IN
= V
DD
= 15V; R
T
= 71 k
; C
T
= 150 pF.
TC18C43
TC28C43
TC38C43
Parameter
Test Conditions
Min
Typ
Max
Min
Typ
Max
Units
Reference Section
Output Voltage
T
A
= 25
C, I
O
= 1mA
4.9
5
5.1
4.90
5
5.10
V
Line Regulation
9.5V
V
IN
15V, I
O
= 1mA
--
3
10
--
3
10
mV
Load Regulation
1mA
l
O
11mA
--
5
15
--
3
10
mV
Temp Stability
(Note 1)
--
0.25
0.5
--
0.25
0.5
mV/
C
Output Noise Voltage
10Hz
f
10 kHz,T
A
= 25
C (Note 1)
--
100
--
--
100
--
V(rms)
Long Term Stability
T
A
= 125
C, 1000 Hrs. (Note 1)
--
0.5
--
--
0.5
--
%
Output Short Circuit
-20
-50
-100
-30
-50
-100
mA
Oscillator Section
Initial Accuracy
T
A
= 25
C (Note 4)
90
100
110
93.8
100
106.5
kHz
Voltage Stability
9.5V
V
IN
15V
--
0.2
0.3
--
0.2
0.3
%
Temp Stability
T
MIN
T
A
T
MAX
(Note 1); Figure 2
--
0.01
0.05
--
0.01
0.03
%/
C
Clock Ramp Reset
R
T
/C
T
Pin at 4V
2.25
2.5
2.75
2.25
2.5
2.75
mA
Amplitude
R
T
/C
T
Pin Peak to Peak
2.45
2.65
2.85
2.45
2.65
2.85
V
Maximum Freq
Note 1
1
--
--
1
--
--
MHz
Error Amp Section
Input Offset Voltage
V
(CMPTR)
= 2.5V
--
15
50
--
15
50
mV
Input Bias Current
(Note 1)
--
0.3
2
--
0.3
2
nA
A
VOL
2V
V
O
4V
70
90
--
70
90
--
dB
Gain Bandwidth Product
(Note 1)
650
750
--
650
750
--
kHz
PSRR
9.5V
V
IN
15V
80
100
--
80
100
--
dB
Output Sink Current
V
FB
= 2.7V, V
(CMPTR)
= 1.1V (Note 1)
1.2
1.5
--
1.5
1.7
--
mA
Output Source Current
V
FB
= 2.3V, V
(CMPTR)
= 5V (Note 1)
3
3.4
--
3.9
4.2
--
mA
V
OUT
High
V
FB
= 2.3V, R
L
= 10k to Ground
5.65
6
6.5
5.65
6
6.5
V
V
OUT
Low
V
FB
= 2.7V, R
L
= 10k to V
REF
0.1
0.7
1.1
0.1
0.7
1.1
V
Rise Response
Note 1
--
5
7
--
5
7
sec
Fall Response
Note 1
--
3
5
--
3
5
sec
Current Sense Section
Gain Ratio
Notes 2 & 3
2.8
2.9
3.1
2.8
2.9
3.1
V/V
Maximum Input Signal
V
(CMPTR)
= 5V (Note 2)
0.85
0.95
1.05
0.85
0.95
1.05
V
PSRR
9.5V
V
IN
15V (Notes 1, 2 & 5)
70
80
--
70
80
--
dB
Input Bias Current
Note 1
--
0.3
2
--
0.3
2
nA
Delay to Output
V
(
I
SENSE)
= 1V (Note 1); Figure 3
--
140
160
--
140
150
nsec
TC18C43
TC28C43
TC38C43
BiCMOS CURRENT MODE
PWM CONTROLLERS
4-95
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
Output Section
R
DS (ON)
I
SINK
= 20mA
--
7
15
--
7
15
R
DS (ON)
I
SOURCE
= 20mA
--
11
20
--
11
15
Rise Time
C
L
= 1nF (Note 1)
--
40
60
--
35
60
nsec
Fall Time
C
L
= 1nF (Note 1)
--
30
60
--
30
40
nsec
Cross Conduction
In Coulombs (Note 1)
--
6.5
--
--
6.5
--
nC
V
DD
Ma
Note 1
--
--
18
--
--
18
V
Undervoltage Lockout Section
Start Threshold
x8C43
7.9
8.4
8.8
7.9
8.4
8.8
V
Undervoltage Threshold
x8C43
7.2
7.6
7.9
7.2
7.6
7.9
V
PWM Section
Maximum Duty Cycle
x8C43 (Note 1)
95
97
100
95
97
100
%
Minimum Duty Cycle
0
0
%
Supply Current
Start Up
T
A
= 25
C, V
IN
< V
UV
; Figure 1
50
170
300
50
170
300
A
Operating
V
FB
= V(I
SENSE
) = 0V; Figure 4
1
2
1
1.5
mA
ELECTRICAL CHARACTERISTICS (Cont):
unless otherwise stated, these specifications apply over specified
temperature range. V
IN
= V
DD
= 15V; R
T
= 71 k
; C
T
= 150 pF.
TC18C4X
TC28C4X
TC38C4X
Parameter
Test Conditions
Min
Typ
Max
Min
Typ
Max
Units
where 0
V(I
SENSE
)
0.8V
4. Output frequency equals oscillator frequency for the
x8C43.
5. PSRR of V
REF
, Error Amp and PWM Comparator
combination.
NOTES: 1. These parameters, although guaranteed over the
recommended operating conditions, are not tested in
production.
2. Parameter measured at trip point of latch.
3. Gain ratio is defined as:
V
COMP
V(I
SENSE
)
TelCom Semiconductor reserves the right to make changes in the circuitry or specifications detailed in this manual at any time without notice. Minimums
and maximums are guaranteed. All other specifications are intended as guidelines only. TelCom Semiconductor assumes no responsibility for the use of
any circuits described herein and makes no representations that they are free from patent infringement.
*Static-sensitive device. Unused devices must be stored in conductive material. Protect devices from static discharge and static fields. Stresses above
those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional operation of
the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to Absolute
Maximum Rating Conditions for extended periods may affect device reliability.
PIN DESCRIPTION
Pin No.
Pin No
Pin No
8-Pin
14-Pin
16-Pin
Symbol
Description
2
1
NC
No Connection
4
2
NC
No Connection
1
1
3
CMPTR
Compensation of the feedback loop response.
2
3
4
V
FB
Feedback of voltage to error amplifier to regulate voltage.
3
5
5
I
SENSE
For sensing pass transistor current and terminate drive when current
limit threshold is reached at this pin.
4
7
6
R
T
/C
T
Capacitor and resistor input to set oscillator frequency of this PWM
controller. The resistor is connected from V
REF
output to R
T
/C
T.
The capacitor is connected from R
T
/C
T
to ANALOG GND.
TC18C43
TC28C43
TC38C43
BiCMOS CURRENT MODE
PWM CONTROLLERS
4-96
TELCOM SEMICONDUCTOR, INC.
TC18C43
TC28C43
TC38C43
BiCMOS CURRENT MODE
PWM CONTROLLERS
Pin No.
Pin No
Pin No
8-Pin
14-Pin
16-Pin
Symbol
Description
PIN DESCRIPTION (Cont.)
6
7
NC
No Connection
13
8
NC
No Connection
9
NC
No Connection
8
10
POWER GROUND
Ground return of output driver.
5
9
11
ANALOG GND
For all the low level analog signal returns.
6
10
12
OUTPUT
Output to drive switching transistor gate input.
11
13
V
DD
Supply power input terminal for the output drivers.
7
12
14
V
IN
Voltage bias supply of all PWM Controller circuit functions.
8
14
15
V
REF
Reference: 5.0 volt output.
16
NC
No Connection.
FREQUENCY OF OPERATION
The frequency of oscillation for the TC38C43 is con-
trolled by a resistor to V
REF
(R
T
) and a capacitor to ground
(C
T
). V
REF
supplies current through the resistor and charges
the capacitor until its voltage reaches the threshold of the
upper comparator (
2.5V). A 2.5mA current is then applied
to the capacitor to discharge it to near ground (
0.15V). The
discharge current is then shut off and the cycle repeats. An
approximate equation for the frequency of operation is:
7
VREF
14
PIN NUMBERS FOR 14-PIN DIP
9
RT/CT
GND
(5V)
RT
CT
REFERENCE SECTION
The reference is a zener-based design with a buffer
amplifier to drive the output. It is unstable with capacitances
between 0.01
F and 3.3
F. In a normal application a 4.7
F
is used. In some lower noise layouts the capacitor can be
eliminated entirely.
The reference is active as soon as the 38C4x has
power supplied. This is different than its bipolar counter-
parts, in that the bipolar reference comes on only after the IC
has come out of its under voltage mode. Thus, on the 38C4x,
the reference pin can not be used as a reset function such
as on a soft start circuit.
OSCILLATOR SECTION
The oscillator frequency is set by the combination of a
resistor from the reference to the R
T
/C
T
pin and by a
capacitor from this pin to ground. The oscillator is designed
to have ramp amplitude from 0.15 to 2.5 volts. This is
approximate, as over shoot on the oscillator comparator
causes the ramp amplitude to increase with frequency due
to comparator delay. Minimum values for C
T
and R
T
are
33pF and 1k
respectively. Maximum values are depen-
dent on leakage currents in the capacitor, not on the input
currents to the R
T
/C
T
pin.
f
O
1 (R
T
in Ohms and C
T
in Farads)
R
T
C
T
The value of R
T
affects the discharge current and the
upper and lower comparators each have delays. As R
T
gets
smaller and as the frequency of operation gets higher, the
above equation is no longer valid.
4-97
TELCOM SEMICONDUCTOR, INC.
7
6
5
4
3
1
2
8
TC18C43
TC28C43
TC38C43
BiCMOS CURRENT MODE
PWM CONTROLLERS
Dead Time
The value of R
T
has an effect on the discharge rate but
the primary consideration is the value of C
T
. The time
required to discharge the capacitor is approximately 1000
C
T
.
Undervoltage Lockout Range
The TCx8C43 PWM Controller is used where wide
ranges of input voltage is not required. The range from
starting V
in
voltage threshold to under voltage threshold is
approximately 9.5% of the starting voltage. The typical start-
up voltage is 8.4V and dropout voltage is 7.6V. This range
is used most in DC-to-DC converter applications.
Duty Cycle Limit
The TCx8C43 PWM Controller has a duty cycle limit
maximum of 99%. The oscillator is running at the same
frequency as the output.
Current is sensed through voltage drop across resistor
RS. A small RC filter may be required to suppress switching
transient. This voltage enters PWM Controller at I
SENSE
,
pin 5. A voltage of 0.4 V is added before this is fed into PWM
Comparator (+) input. The PWM Comparator () input
senses the voltage feedback error amp output with a limit
buffer that limits this voltage to 1.4V maximum. This limit
buffer limits the peak current across RS to a maximum of
0.95V. In normal operation, the error amplifier controls the
current limit threshold.
Shutdown can be accomplished by either pulling I
SENSE
above 1 volt or pulling CMPTR, pin 1 to GND. This will set the
PWM latch so that the output will remain low until the next
clock pulse after the shutdown condition is removed.
SHUTDOWN METHODS
TCx8C43
VON = 8.4V
VOFF = 7.6V
IS
7.6V
8.4 V
1mA
170
A
VDD
VIN
TCx8C43
ERROR AMP
+
LIMIT BUFFER
+
1.4V
2R
R
GND
+
C
R
ISENSE
5
0.4V
PWM
COMPARATOR
9
RS
PEAK CURRENT (IS) FORMULA:
IS =
0.95V
RS
CURRENT SENSE CIRCUIT
ISENSE
5
TCx38C43
VREF
SHUTDOWN
14
TO CURRENT
SENSE RESISTOR
5k
5.1k
9
TCx38C43
SHUTDOWN
ANALOG
GND
CMPTR
1
BENCH TEST OPERATIONAL SIMULATION
The timing ramp (R
T
/C
T
) is buffered by the emitter
fullpower and fed back to the I
SENSE
input. This ramp
simulates the dI/dT current ramp which would flow through
the primary of the transformer. The output voltage of the
power supply is simulated by feeding some of the reference
voltage into V
FB
. The combination of the two levels deter-
mined the operating characteristics of the current mode
controller.
UNDERVOLTAGE LOCKOUT RANGE