TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C JUNE 1976 REVISED AUGUST 1995
Copyright
1995, Texas Instruments Incorporated
41
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
High Efficiency . . . 60% or Greater
Output Current . . . 500 mA
Input Current Limit Protection
TTL-Compatible Inhibit
Adjustable Output Voltage
Input Regulation . . . 0.2% Typ
Output Regulation . . . 0.4% Typ
Soft Start-Up Capability
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, CT (pF)
200
250
350
400
500
750
1000
1500
2000
ON TIME (
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
T
PACKAGED DEVICES
CHIP
TA
SURFACE MOUNT
(D)
PLASTIC DIP
(N)
SHRINK
SMALL OUTLINE
(PW)
CHIP
FORM
(Y)
0
C to 70
C
TL497ACD
TL497ACN
TL497ACPW
TL497AY
40
C to 85
C
TL497AID
TL497AIN
--
--
1
2
3
4
5
6
7
14
13
12
11
10
9
8
COMP INPUT
INHIBIT
FREQ CONTROL
SUBSTRATE
GND
CATHODE
ANODE
V
CC
CUR LIM SENS
BASE DRIVE
BASE
COL OUT
NC
EMIT OUT
(TOP VIEW)
TL497AC, TL497AI . . . D, N, OR PW PACKAGE
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.
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.
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C JUNE 1976 REVISED AUGUST 1995
42
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
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
FREQ CONTROL
INHIBIT
SUBSTRATE
COMP INPUT
CATHODE
Current
Limit
Sense
13
3
2
1
4
6
1.2-V
Reference
10
8
7
COL OUT
EMIT OUT
ANODE
Oscillator
BASE and BASE DRIVE are used for device testing only. They are not normally used in circuit applications of the device.
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C JUNE 1976 REVISED AUGUST 1995
43
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
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
FREQ CONTROL
COMP INPUT
SUBSTRATE
CATHODE
CUR
LIM
SENS
BASE
DRIVE BASE
GND
V
CC
TL497AY
COL
OUT
EMIT
OUT
ANODE
(13)
(12)
(11)
(3)
(2)
(1)
(4)
(6)
(8)
(7)
(10)
(14)
(5)
CHIP THICKNESS: 15 MILS TYPICAL
BONDING PADS: 4
4 MILS MINIMUM
TJmax= 150
C
TOLERANCES ARE
10%
ALL DIMENSIONS ARE IN MILS
INHIBIT
68
115
BASE (11) and BASE DRIVE (12) are used for device testing
only. They are not normally used in circuit applications of the
device.
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(14)
(10)
(11)
(12)
(13)
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C JUNE 1976 REVISED AUGUST 1995
44
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, V
CC
(see Note 1)
15 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output voltage, V
O
35 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage, V
I
(COMP INPUT)
5 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input voltage, V
I
(INHIBIT)
5 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diode reverse voltage
35 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power switch current
750 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diode forward current
750 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous total power dissipation
See Dissipation Rating Table
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range, T
A
: TL497AC
0
C to 70
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TL497AI
40
C to 85
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, T
stg
65
C to 150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lead temperature 1,6 mm (1/16 inch) from case for 60 seconds
260
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.
DISSIPATION RATING TABLE
PACKAGE
TA
25
C
POWER RATING
DERATING
FACTOR
DERATE
ABOVE TA
TA = 70
C
POWER RATING
TA = 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, VCC
4.5
12
V
High-level input voltage, VIH, INHIBIT
2.5
V
Low-level input voltage, VIL, INHIBIT
0.8
V
O
l
Step-up configuration (see Figure 1)
VI + 2
30
V
Output voltage
Step-down configuration (see Figure 2)
Vref
VI 1
V
p
g
Inverting regulator (see Figure 3)
Vref
25
Power switch current
500
mA
Diode forward current
500
mA
Operating free-air temperature TA
TL497AC
0
70
C
Operating free-air temperature, TA
TL497AI
40
85
C
TL497AC, TL497AI, TL497AY
SWITCHING VOLTAGE REGULATORS
SLVS009C JUNE 1976 REVISED AUGUST 1995
45
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
electrical characteristics over recommended operating conditions, V
CC
= 6 V (unless otherwise
noted)
PARAMETER
TEST CONDITIONS
TA
TL497AC
TL497AI
UNIT
PARAMETER
TEST CONDITIONS
TA
MIN
TYP
MAX
MIN
TYP
MAX
UNIT
High-level input current, INHIBIT
VI(I) = 5 V
Full range
0.8
1.5
0.8
1.5
mA
Low-level input current, INHIBIT
VI(I) = 0 V
Full range
5
10
5
20
A
Comparator reference voltage
VI = 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
VI = 6 V
Full range
40
100
40
100
A
Switch on-state voltage
VI = 4 5 V
IO = 100 mA
25
C
0.13
0.2
0.13
0.2
V
Switch on-state voltage
VI = 4.5 V
IO = 500 mA
Full range
0.85
1
V
Switch off-state current
VI = 4 5 V
VO = 30 V
25
C
10
50
10
50
A
Switch off-state current
VI = 4.5 V,
VO = 30 V
Full range
200
500
A
Sense voltage, CUR LIM SENS
VI = 6 V
25
C
0.45
1
0.45
1
V
Di d f
d
l
IO = 10 mA
Full range
0.75
0.85
0.75
0.95
V
Diode forward voltage
IO = 100 mA
Full range
0.9
1
0.9
1.1
V
g
IO = 500 mA
Full range
1.33
1.55
1.33
1.75
Diode reverse voltage
IO = 500
A
Full range
30
V
Diode reverse voltage
IO = 200
A
Full range
30
V
On-state supply current
25
C
11
14
11
14
mA
On-state supply current
Full range
15
16
mA
Off-state supply current
25
C
6
9
6
9
mA
Off-state supply current
Full range
10
11
mA
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 TA = 25
C.
electrical characteristics over recommended operating conditions, V
CC
= 6 V, T
A
= 25
C (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
TL497AY
UNIT
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
High-level input current, INHIBIT
VI(I) = 5 V
0.8
mA
Low-level input current, INHIBIT
VI(I) = 0 V
5
A
Comparator reference voltage
VI = 4.5 V to 6 V
1.2
V
Comparator input bias current
VI = 6 V
40
A
Switch on-state voltage
VI = 4.5 V,
IO = 100 mA
0.13
V
Switch off-state current
VI = 4.5 V,
VO = 30 V
10
A
Di d f
d
l
IO = 10 mA
0.75
V
Diode forward voltage
IO = 100 mA
0.9
V
g
IO = 500 mA
1.33
On-state supply current
11
mA
Off-state supply current
6
mA
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