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TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C – JUNE 1976 – REVISED AUGUST 1995
•
High Efficiency...60% or Greater
TL497AC, TL497AI . . . D, N, OR PW PACKAGE
(TOP VIEW)
•
Output Current...500 mA
•
Input Current Limit Protection
COMP INPUT
INHIBIT
FREQ CONTROL
SUBSTRATE
GND
CATHODE
ANODE
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V CC
CUR LIM SENS
BASE DRIVE †
BASE †
COL OUT
NC
EMIT OUT
•
TTL-Compatible Inhibit
•
Adjustable Output Voltage
•
Input Regulation...0.2% Typ
•
Output Regulation...0.4% Typ
•
Soft Start-Up Capability
NC – No internal connection
† BASE (11) and BASE DRIVE (12) are used for device testing only.
They are not normally used in circuit applications of the device.
description
The TL497AC and TL497AI incorporate on a single monolithic chip all the active functions required in the
construction of switching voltage regulators. They can also be used as the control element to drive external
components for high-power-output applications. The TL497AC and TL497AI were designed for ease of use in
step-up, step-down, or voltage inversion applications requiring high efficiency.
The TL497AC and TL497AI are fixed-on-time variable-frequency switching-voltage-regulator control circuits.
The switch-on time is programmed by a single external capacitor connected between FREQ CONTROL and
GND. This capacitor, C T , is charged by an internal constant-current generator to a predetermined threshold. The
charging current and the threshold vary proportionally with V CC . Thus, the switch-on time remains constant over
the specified range of input voltage (4.5 V to 12 V). Typical on times for various values of C T are as follows:
TIMING CAPACITOR, C T (pF)
200
250
350
400
500
750
1000
1500
2000
ON TIME ( m s)
19
22
26
32
44
56
80
120
180
The output voltage is controlled by an external resistor ladder network (R1 and R2 in Figures 1, 2, and 3) that
provides a feedback voltage to the comparator input. This feedback voltage is compared to the reference
voltage of 1.2 V (relative to SUBSTRATE) by the high-gain comparator. When the output voltage decays below
the value required to maintain 1.2 V at the comparator input, the comparator enables the oscillator circuit, which
charges and discharges C T as described above. The internal pass transistor is driven on during the charging
of C T . The internal transistor may be used directly for switching currents up to 500 mA. Its collector and emitter
are uncommitted, and it is current driven to allow operation from the positive supply voltage or ground. An
internal Schottky diode matched to the current characteristics of the internal transistor is also available for
blocking or commutating purposes. The TL497AC and TL497AI also have on-chip current-limit circuitry that
senses the peak currents in the switching regulator and protects the inductor against saturation and the pass
transistor against overstress. The current limit is adjustable and is programmed by a single sense resistor, R CL ,
connected between V CC and CUR LIM SENS. The current-limit circuitry is activated when 0.7 V is developed
across R CL . External gating is provided by the INHIBIT input. When the INHIBIT input is high, the output is turned
off.
AVAILABLE OPTIONS
PACKAGED DEVICES
CHIP
CHIP
FORM
(Y)
T A
SURFACE MOUNT
(D)
PLASTIC DIP
(N)
SHRINK
SMALL OUTLINE
(PW)
0 ° C to 70 ° C
TL497ACD
TL497ACN
TL497ACPW
TL497AY
–40 ° C to 85 ° C
TL497AID
TL497AIN
—
—
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright
W
1995, Texas Instruments Incorporated
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
4–1
T
11072737.009.png
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C – JUNE 1976 – REVISED AUGUST 1995
description (continued)
Simplicity of design is a primary feature of the TL497AC and TL497AI. With only six external components (three
resistors, two capacitors, and one inductor), the TL497AC and TL497AI operates in numerous voltage
conversion applications (step-up, step-down, invert) with as much as 85% of the source power delivered to the
load. The TL497AC and TL497AI replace the TL497 in all applications.
The TL497AC is characterized for operation from 0
°
C to 70
C, and the TL497AI is characterized for operation
from – 40
°
C to 85
C.
functional block diagram
BASE †
11
12
BASE DRIVE †
CUR LIM SENS
13
Current
Limit
Sense
FREQ CONTROL
INHIBIT
3
2
1
Oscillator
COMP INPUT
10
COL OUT
SUBSTRATE
4
1.2-V
Reference
8
EMIT OUT
CATHODE
6
7
ANODE
† BASE and BASE DRIVE are used for device testing only. They are not normally used in circuit applications of the device.
4–2
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
°
°
11072737.010.png 11072737.011.png
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C – JUNE 1976 – REVISED AUGUST 1995
TL497AY chip information
This chip, when properly assembled, displays characteristics similar to the TL497AC. Thermal compression or
ultrasonic bonding may be used on the doped aluminum bonding pads. The chips may be mounted with
conductive epoxy or a gold-silicon preform.
BONDING PAD ASSIGNMENTS
(13)
(12)
(11)
(10)
(8)
(14)
CHIP THICKNESS: 15 MILS TYPICAL
BONDING PADS: 4 × 4 MILS MINIMUM
68
T J max= 150 ° C
TOLERANCES ARE ± 10%
ALL DIMENSIONS ARE IN MILS
(1)
(2) (3)
(4) (5) (6)
(7)
115
CUR
LIM
SENS
BASE
DRIVE †
BASE †
(13)
(12)
(11)
(3)
(2)
(1)
(4)
(6)
FREQ CONTROL
(10)
COL
OUT
EMIT
OUT
INHIBIT
COMP INPUT
SUBSTRATE
CATHODE
TL497AY
(8)
(7)
ANODE
(5)
(14)
GND V CC
† BASE (11) and BASE DRIVE (12) are used for device testing
only. They are not normally used in circuit applications of the
device.
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
4–3
11072737.012.png 11072737.001.png
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C – JUNE 1976 – REVISED AUGUST 1995
absolute maximum ratings over operating free-air temperature range (unless otherwise noted) †
Supply voltage, V CC (see Note 1)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage, V I (COMP INPUT)
35 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 V
Input voltage, V I (INHIBIT)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 V
Diode reverse voltage
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35 V
Power switch current
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
750 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous total power dissipation
750 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range, T A : TL497AC
See Dissipation Rating Table
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0
°
C to 70
°
C
TL497AI
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
– 40
°
C to 85
°
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lead temperature 1,6 mm (1/16 inch) from case for 60 seconds
–65
°
C to 150
°
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
† Stresses beyond 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 beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: All voltage values except diode voltages are with respect to network ground terminal.
260
°
C
DISSIPATION RATING TABLE
PACKAGE
T A 3 25 ° C
POWER RATING
DERATING
FACTOR
DERATE
ABOVE T A
T A = 70 ° C
POWER RATING
T A = 85 ° C
POWER RATING
D
950 mW
7.6 mW/
C
25
C
608 mW
494 mW
N
1000 mW
9.2 mW/ ° C
41 ° C
733 mW
595 mW
PW
700 mW
5.6 mW/
C
25
C
448 mW
—
recommended operating conditions
MIN
MAX UNIT
Supply voltage, V CC
4.5
12
V
High-level input voltage, V IH, INHIBIT
2.5
V
Low-level input voltage, V IL, INHIBIT
0.8
V
Step-up configuration (see Figure 1)
V I + 2
30
Output voltage Step-down configuration (see Figure 2)
l
V ref V I – 1
V
Inverting regulator (see Figure 3)
–V ref
–25
Power switch current
500
mA
Diode forward current
500
mA
Operating free-air temperature, T A
TL497AC
0
70
° C
° C
TL497AI
–40
85
4–4
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
Output voltage, V O
Diode forward current
Storage temperature range, T stg
°
°
°
°
O
V
Operating free-air temperature T A
11072737.002.png 11072737.003.png
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C – JUNE 1976 – REVISED AUGUST 1995
electrical characteristics over recommended operating conditions, V CC = 6 V (unless otherwise
noted)
TEST CONDITIONS
TL497AC
TL497AI
PARAMETER
TEST CONDITIONS
T A †
UNIT
PARAMETER
UNIT
MIN TYP ‡
MIN TYP ‡
MAX
MAX
High-level input current, INHIBIT V I(I) = 5 V
Full range
0.8
1.5
0.8
1.5
mA
Low-level input current, INHIBIT V I(I) = 0 V
Full range
5
10
5
20
m
A
Comparator reference voltage
V I = 4.5 V to 6 V
Full range
1.08
1.2
1.32
1.14
1.2
1.26
V
Comparator input bias current
V I = 6 V
Full range
40
100
40
100
m
A
I O = 100 mA
25 ° C
0.13
0.2
0.13
0.2
Switch on-state voltage
V I = 4.5 V
V
V
I O = 500 mA Full range
0.85
1
Switch off-state current
V I = 4.5 V, V O = 30 V
25 ° C
10
50
10
50
m
A
Switch off-state current
V I =45V V O =30V
m
A
Full range
200
500
Sense voltage, CUR LIM SENS V I = 6 V
25 ° C
0.45
1
0.45
1
V
I O = 10 mA
Full range
0.75
0.85
0.75
0.95
Diode forward voltage
d l
I O = 100 mA
Full range
0.9
1
0.9
1.1
V
I O = 500 mA
Full range
1.33
1.55
1.33
1.75
Diode reverse voltage
I O = 500
m
A
Full range
30
Diode reverse voltage
V
V
I O = 200 m A
Full range
30
25
°
C
11
14
11
14
On-state supply current
mA
Full range
15
16
25
°
C
6
9
6
9
Off-state supply current
mA
Full range
10
11
† Full range for the TL497AC is 0
°
C to 70
C and full range for the TL497AI is – 40
°
C to 85
°
C.
‡ All typical values are at T A = 25
°
C.
electrical characteristics over recommended operating conditions, V CC = 6 V, T A = 25
°
C (unless
TL497AY
PARAMETER
TEST CONDITIONS
UNIT
PARAMETER
UNIT
MIN
TYP
MAX
High-level input current, INHIBIT
V I(I) = 5 V
0.8
mA
Low-level input current, INHIBIT
V I(I) = 0 V
5
m
A
Comparator reference voltage
V I = 4.5 V to 6 V
1.2
V
Comparator input bias current
V I = 6 V
40
m A
Switch on-state voltage
V I = 4.5 V,
I O = 100 mA
0.13
V
Switch off-state current
V I = 4.5 V,
V O = 30 V
10
m A
I O = 10 mA
0.75
Diode forward voltage
d l
I O = 100 mA
0.9
V
I O = 500 mA
1.33
On-state supply current
11
mA
Off-state supply current
6
mA
POST OFFICE BOX 655303
•
DALLAS, TEXAS 75265
4–5
T A †
Switch on-state voltage
V I =45V
Di d f
V
On-state supply current
mA
Off-state supply current
mA
°
otherwise noted)
TEST CONDITIONS
Di d f
V
11072737.004.png 11072737.005.png 11072737.006.png 11072737.007.png 11072737.008.png

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