LTC1159
LTC1159-3.3/LTC1159-5
High Efficiency Synchronous
Step-Down Switching Regulators
FEATURES
s
s
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s
s
DESCRIPTIO
s
s
s
s
s
Operation from 4V to 40V Input Voltage
Ultrahigh Efficiency: Up to 95%
20
µ
A Supply Current in Shutdown
High Efficiency Maintained Over Wide Current Range
Current Mode Operation for Excellent Line and Load
Transient Response
Very Low Dropout Operation: 100% Duty Cycle
Short-Circuit Protection
Synchronous FET Switching for High Efficiency
Adaptive Non-Overlap Gate Drives
Available in SSOP and SO Packages
The LTC
®
1159 series is a family of synchronous step-down
switching regulator controllers featuring automatic Burst
Mode
TM
operation to maintain high efficiencies at low
output currents. These devices drive external complemen-
tary power MOSFETs at switching frequencies up to 250kHz
using a constant off-time current-mode architecture.
A separate pin and on-board switch allow the MOSFET
driver power to be derived from the regulated output
voltage providing significant efficiency improvement when
operating at high input voltages. The constant off-time
current-mode architecture maintains constant ripple cur-
rent in the inductor and provides excellent line and load
transient response. The output current level is user pro-
grammable via an external current sense resistor.
The LTC1159 automatically switches to power saving
Burst Mode operation when load current drops below
approximately 15% of maximum current. Standby current
is only 300µA while still regulating the output and shut-
down current is a low 20µA.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
APPLICATIO S
s
s
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s
s
s
s
Step-Down and Inverting Regulators
Notebook and Palmtop Computers
Portable Instruments
Battery-Operated Digital Devices
Industrial Power Distribution
Avionics Systems
Telecom Power Supplies
TYPICAL APPLICATIO
V
IN
CAP
0.15µF
V
IN
+
1N4148
P-GATE
0.1µF
P-DRIVE
EXTV
CC
LTC1159-5
0V = NORMAL
>2V = SHUTDOWN
3300pF
1k
C
T
300pF
SHDN1
SHDN2
I
TH
C
T
S-GND
SENSE
+
Si9435DY
C
IN
100µF
100V
+
3.3µF
V
CC
V
CC
EFFICIENCY (%)
D1
MBRS140T3
L*
33µH
3
R
SENSE
1
0.05Ω
2
4
V
OUT
5V/2A
SENSE
–
N-GATE
P-GND
0.01µF
+
Si9410DY
C
OUT
220µF
60
0.02
LTC1159 • F01
*COILTRONICS CTX33-4-MP
Figure 1. High Efficiency Step-Down Regulator
U
LTC1159-5 Efficiency
100
FIGURE 1 CIRCUIT
V
IN
= 10V
90
V
IN
= 20V
80
70
0.2
LOAD CURRENT (A)
2
LTC1159 • TA01
U
U
1
LTC1159
LTC1159-3.3/LTC1159-5
ABSOLUTE
AXI U
RATI GS
Input Supply Voltage (Pin 2) ..................... – 15V to 60V
V
CC
Output Current (Pin 3) .................................. 50mA
Continuous Pin Currents (Any Pin) ...................... 50mA
Sense Voltages ......................................... – 0.3V to 13V
Shutdown Voltages ................................................... 7V
EXTV
CC
Input Voltage ............................................. 15V
Junction Temperature (Note 2) ............................ 125°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
P-GATE
V
IN
V
CC
P-DRIVE
P-DRIVE
V
CC
V
CC
C
T
I
TH
SENSE
–
1
2
3
4
5
6
7
8
9
10
20 CAP
19 SHDN2
18 EXTV
CC
17 PGND
16 N-GATE
15 PGND
14 SGND
13 SHDN1
12 V
FB
11 SENSE
+
ORDER PART
NUMBER
LTC1159CG
LTC1159CG-3.3
LTC1159CG-5
G PACKAGE
20-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 135°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
SHDN1
= 0V (Note 3), unless otherwise noted.
SYMBOL
V
FB
I
FB
V
OUT
∆V
OUT
PARAMETER
Feedback Voltage (LTC1159 Only)
Feedback Current (LTC1159 Only)
Regulated Output Voltage
LTC1159-3.3
LTC1159-5
Output Voltage Line Regulation
Output Voltage Load Regulation
LTC1159-3.3
LTC1159-5
Burst Mode Output Ripple
I
IN
V
IN
Pin Current (Note 4)
Normal Mode
Shutdown
I
EXTVCC
EXTV
CC
Pin Current (Note 4)
V
IN
= 9V
I
LOAD
= 700mA
I
LOAD
= 700mA
V
IN
= 9V to 40V
5mA < I
LOAD
< 2A
5mA < I
LOAD
< 2A
I
LOAD
= 0A
V
IN
= 12V, EXTV
CC
= 5V
V
IN
= 40V, EXTV
CC
= 5V
V
IN
= 12V, V
SHDN2
= 2V
V
IN
= 40V, V
SHDN2
= 2V
EXTV
CC
= 5V, Sleep Mode
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
q
q
q
q
2
U
U
W
W W
U
W
(Note 1)
Operating Temperature Range
LTC1159C .............................................. 0°C to 70°C
LTC1159I ........................................... – 40°C to 85°C
Extended Commercial
Temperature Range ............................... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
TOP VIEW
P-GATE
V
IN
V
CC
P-DRIVE
V
CC
C
T
I
TH
SENSE
–
1
2
3
4
5
6
7
8
16 CAP
15 SHDN2
14 EXTV
CC
13 N-GATE
12 PGND
11 SGND
10 V
FB
(SHDN1)*
9
SENSE
+
ORDER PART
NUMBER
LTC1159CN
LTC1159CN-3.3
LTC1159CN-5
LTC1159CS
LTC1159CS-3.3
LTC1159CS-5
LTC1159IS
LTC1159IS-3.3
LTC1159IS-5
N PACKAGE
16-LEAD PDIP
S PACKAGE
16-LEAD PLASTIC SO
*FIXED OUTPUT VERSIONS
T
JMAX
= 125°C,
θ
JA
= 80°C/ W (N)
T
JMAX
= 125°C,
θ
JA
= 110°C/ W (S)
MIN
1.21
TYP
1.25
0.2
MAX
1.29
UNITS
V
µA
3.23
4.90
– 40
3.33
5.05
0
40
60
50
200
300
15
25
250
3.43
5.20
40
65
100
V
V
mV
mV
mV
mV
P-P
µA
µA
µA
µA
µA
LTC1159
LTC1159-3.3/LTC1159-5
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
SHDN1
= 0V (Note 3), unless otherwise noted.
SYMBOL
V
CC
V
IN
– V
CC
V
EXT
– V
CC
PARAMETER
Internal Regulator Voltage
V
CC
Dropout Voltage
EXTV
CC
Switch Drop
CONDITIONS
V
IN
= 12V to 40V, EXTV
CC
= 0V, I
CC
= 10mA
V
IN
= 4V, EXTV
CC
= Open, I
CC
= 10mA
V
IN
= 12V, EXTV
CC
= 5V, I
SWITCH
= 10mA
V
IN
= 12V
V
IN
= 40V
V
SENSE –
= 5V, V
FB
= 1.32V (Forced)
V
SENSE –
= 5V, V
FB
= 1.15V (Forced)
V
SENSE –
= 3.4V (Forced)
V
SENSE –
= 3.1V (Forced)
V
SENSE –
= 5.2V (Forced)
V
SENSE –
= 4.7V (Forced)
– 0.2
– 0.2
q
ELECTRICAL CHARACTERISTICS
MIN
4.25
TYP
4.5
300
250
0
0
25
150
25
150
25
150
0.8
1.4
12
70
2
5
100
MAX
4.75
400
350
UNITS
V
mV
mV
V
V
mV
mV
mV
mV
mV
mV
V
V
µA
µA
µA
µs
ns
V
P-GATE
– V
IN
P-Gate to Source Voltage (Off)
V
SENSE +
–
V
SENSE –
Current Sense Threshold Voltage
LTC1159
LTC1159-3.3
LTC1159-5
V
SNDN1
V
SHDN2
I
SHDN2
I
CT
t
OFF
t
r
, t
f
SHDN1 Threshold
LTC1159CG, LTC1159-3.3, LTC1159-5
SHDN2 Threshold
Shutdown 2 Input Current
C
T
Pin Discharge Current
Off-Time (Note 5)
Driver Output Transition Times
q
q
q
130
130
130
0.5
0.8
170
170
170
2
2
20
90
10
6
200
V
SHDN2
= 5V
V
OUT
in Regulation
V
OUT
= 0V
C
T
= 390pF, I
LOAD
= 700mA, V
IN
= 10V
C
L
= 3000pF (Pins P-Drive and N-Gate), V
IN
= 6V
50
4
– 40°C
≤
T
A
≤
85°C (Note 6)
SYMBOL
V
FB
V
OUT
PARAMETER
Feedback Voltage (LTC1159 Only)
Regulated Output Voltage
LTC1159-3.3
LTC1159-5
V
IN
Pin Current (Note 4)
Normal
Shutdown
I
EXTVCC
V
CC
V
SENSE +
–
V
SENSE –
V
SHDN2
t
OFF
EXTV
CC
Pin Current (Note 4)
Internal Regulator Voltage
Current Sense Threshold Voltage
SHDN2 Threshold
Off-Time (Note 5)
C
T
= 390pF, I
LOAD
= 700mA, V
IN
= 10V
V
IN
= 9V
I
LOAD
= 700mA
I
LOAD
= 700mA
V
IN
= 12V, EXTV
CC
= 5V
V
IN
= 40V, EXTV
CC
= 5V
V
IN
= 12V, V
SHDN2
= 2V
V
IN
= 40V, V
SHDN2
= 2V
EXTV
CC
= 5V, Sleep Mode
V
IN
= 12V to 40V, EXTV
CC
= 0V, I
CC
= 10mA
Low Threshold (Forced)
High Threshold (Forced)
CONDITIONS
MIN
1.2
3.17
4.85
TYP
1.25
3.30
5.05
200
300
15
25
250
4.5
25
150
1.4
5
MAX
1.3
3.43
5.25
UNITS
V
V
V
µA
µA
µA
µA
µA
V
mV
mV
V
µs
I
IN
125
0.8
3.5
175
2
6.5
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC1159CG, LTC1159CG-3.3, LTC1159CG-5: T
J
= T
A
+ (P
D
• 135°C/W)
LTC1159CN, LTC1159CN-3.3, LTC1159CN-5: T
J
= T
A
+ (P
D
• 80°C/W)
LTC1159CS, LTC1159CS-3.3, LTC1159CS-5: T
J
= T
A
+ (P
D
• 110°C/W)
Note 3:
On LTC1159 versions which have a SHDN1 pin, it must be at
ground potential for testing.
Note 4:
The LTC1159 V
IN
and EXTV
CC
current measurements exclude
MOSFET driver currents. When V
CC
power is derived from the output via
EXTV
CC
, the input current increases by (I
GATECHG
• Duty Cycle)/(Efficiency).
See Typical Performance Characteristics and Applications Information.
Note 5:
In applications where R
SENSE
is placed at ground potential, the off-
time increases approximately 40%.
3
LTC1159
LTC1159-3.3/LTC1159-5
ELECTRICAL CHARACTERISTICS
Note 6:
The LTC1159C, LTC1159C-3.3, and LTC1159C-5 are not tested
and not quality assurance sampled at – 40°C and 85°C. These
specifications are guaranteed by design and/or correlation. The LTC1159I,
LTC1159I-3.3 and LTC1159I-5 are guaranteed and tested over the – 40°C
to 85°C operating temperature range.
Note 7:
The logic-level power MOSFETs shown in Figure 1 are rated for
V
DS(MAX)
= 30V. For operation at V
IN
> 30V, use standard threshold
MOSFETs with EXTV
CC
powered from a 12V supply. See Applications
Information.
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Input Voltage
100
FIGURE 1 CIRCUIT
I
LOAD
= 1A
95
EFFICIENCY (%)
∆V
OUT
(mV)
90
NOTE 6
0
–20
∆V
OUT
(mV)
85
80
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
EXTV
CC
Pin Current
10
500
FIGURE 1 CIRCUIT
400
I
LOAD
= 1A
6
NOTE 6
4
I
LOAD
= 100mA
2
I
LOAD
= 0
0
0
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
SUPPLY CURRENT (µA)
NORMALIZED FREQUENCY
8
EXTV
CC
CURRENT (mA)
4
U W
LTC1159 • TPC01
Line Regulation
60
40
20
NOTE 6
FIGURE 1 CIRCUIT
I
LOAD
= 1A
20
0
–20
–40
–60
–80
–100
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
Load Regulation
FIGURE 1 CIRCUIT
V
IN
= 24V
–40
–60
0
0.5
1.0
1.5
2.0
LOAD CURRENT (A)
2.5
LT1159 • TPC02
LTC1159 • TPC03
V
IN
Pin Current
FIGURE 1 CIRCUIT
2.0
Operating Frequency
vs (V
IN
– V
OUT
)
V
OUT
= 5V
T = 0°C
1.5
T = 25°C
T = 70°C
1.0
300
NORMAL
200
NOTE 6
100
V
SHDN2
= 2V
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
0.5
0
0
5
15
20
10
(V
IN
– V
OUT
) VOLTAGE (V)
25
LTC1159 • TPC04
LTC1159 • TPC05
LTC1159 • TPC06
LTC1159
LTC1159-3.3/LTC1159-5
TYPICAL PERFOR A CE CHARACTERISTICS
EXTV
CC
Switch Drop
600
500
OFF-TIME (µs)
400
300
200
100
50
40
30
20
10
LTC1159-5
LTC1159-3.3
3
4
2
OUTPUT VOLTAGE (V)
SENSE VOLTAGE (mV)
EXTV
CC
– V
CC
(mV)
0
0
5
10
15
SWITCH CURRENT (mA)
20
PI FU CTIO S
V
IN
:
Main Supply Input Pin.
SGND:
Small-Signal Ground. Must be routed separately
from other grounds to the (–) terminal of C
OUT
.
PGND:
Driver Power Grounds. Connect to source of N-
channel MOSFET and the (–) terminal of C
IN
.
V
CC
:
Outputs of internal 4.5V linear regulator, EXTV
CC
switch, and supply inputs for driver and control circuits.
The driver and control circuits are powered from the higher
of the 4.5V regulator or EXTV
CC
voltage. Must be closely
decoupled to power ground.
C
T
:
External capacitor C
T
from this pin to ground sets the
operating frequency. (The frequency is also dependent on
the ratio V
OUT
/V
IN
.)
I
TH
:
Gain Amplifier Decoupling Point. The current com-
parator threshold increases with the I
TH
pin voltage.
V
FB
:
For the LTC1159 adjustable version, the V
FB
pin
receives the feedback voltage from an external resistive
divider used to set the output voltage.
SENSE
–
:
Connects to internal resistive divider which sets
the output voltage in fixed output versions. The SENSE
–
pin
is also the (–) input of the current comparator.
SENSE
+
:
The (+) Input for the Current Comparator. A built-
in offset between the SENSE
+
and SENSE
–
pins, in conjunc-
tion with R
SENSE
, sets the current trip threshold.
N-Gate:
High Current Drive for the Bottom N-Channel
MOSFET. The N-Gate pin swings from ground to V
CC
.
P-Gate:
Level-Shifted Gate Drive Signal for the Top
P-Channel MOSFET. The voltage swing at the P-gate pin is
from V
IN
to V
IN
– V
CC
.
P-Drive:
High Current Gate Drive for the Top P-Channel
MOSFET. The P-drive pin(s) swing(s) from V
CC
to ground.
CAP:
Charge Compensation Pin. A capacitor to V
CC
pro-
vides charge required by the P-gate level-shift capacitor
during supply transitions.
The charge compensation ca-
pacitor must be larger than the gate drive capacitor.
SHDN1:
This pin shuts down the control circuitry only (V
CC
is not affected). Taking SHDN1 pin high turns off the
control circuitry and holds both MOSFETs off. This pin
must be at ground potential for normal operation.
SHDN2:
Master Shutdown Pin. Taking SHDN2 high shuts
down V
CC
and all control circuitry.
U W
LTC1159 • TPC07
Off-Time vs V
OUT
80
70
60
160
140
120
100
80
60
40
20
Current Sense Threshold Voltage
MAXIMUM
THRESHOLD
MINIMUM
THRESHOLD
0
0
1
5
0
0
20
60
40
TEMPERATURE (°C)
80
100
LTC1159 • TPC08
LTC1159 • TPC09
U
U
U
5
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