LTC1143/LTC1143L
LTC1143L-ADJ
Dual High Efficiency SO-16
Step-Down Switching Regulator
Controllers
DESCRIPTION
The LTC1143 series is a dual step-down switching regulator
controller featuring automatic Burst Mode
TM
operation to
maintain high efficiencies at low output currents. This
device is composed of two separate regulator blocks,
each driving an external power MOSFET at switching
frequencies up to 400kHz using a constant off-time current
mode architecture. Both fixed and adjustable voltages are
available.
The operating current level for both regulators is user-
programmable via an external current sense resistor.
Wide input supply range allows operation from 4V to 14V
(16V maximum). The LTC1143L and LTC1143L-ADJ
extend operation to V
IN
= 3.5V. 100% duty cycle provides
low dropout regulation limited only by the R
DS(ON)
of the
external MOSFET and resistance of the inductor and
current sense resistor.
The LTC1143 series is ideal for applications requiring dual
output voltages with high conversion efficiencies over a
wide load current range in a small amount of board space.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
FEATURES
s
s
s
s
s
s
s
s
s
Dual Outputs
LTC1143, LTC1143L: 3.3V, 5V
LTC1143L-ADJ: Dual Adjustable
Very High Efficiency: Over 95% Possible
Current Mode Operation for Excellent Line and Load
Transient Response
High Efficiency Maintained over Three Decades of
Output Current
Low Standby Current at Light Loads: 160µA/Output
Logic-Controlled Shutdown (LTC1143, LTC1143L)
Wide V
IN
Range: 3.5V to 16V
(LTC1143L, LTC1143L-ADJ)
Very Low Dropout Operation: 100% Duty Cycle
Available in Narrow 16-Pin SO Package
APPLICATIONS
s
s
s
s
s
Personal Digital Assistants
Notebook and Palmtop Computers
Battery-Operated Digital Devices
Portable Instruments
DC Power Distribution Systems
TYPICAL APPLICATION
+
C
IN1
22µF
25V
×
2
0.22µF
P1A
4
1
1000pF
C
OUT1
220µF
10V
×
2
13
V
IN1
P-DRIVE 1
SENSE
+
1
V
IN
4V TO 14V
5
V
IN2
P-DRIVE 2
SENSE
+
2
LTC1143L-ADJ
SENSE
–
2
V
OUT1
3.3V/2A
R
SENSE1
0.05Ω
L1
27µH
+
R2
82.5k
1%
16
D1
MBRS320T3
2
100pF
SENSE
–
1
V
FB1
GND1
3
C
T1
14
I
TH1
15
R
C1
1k
C
C1
C
C2
3300pF 3300pF
I
TH2
7
R
C2
1k
C
T2
300pF
C
T2
6
V
FB2
GND2
11
R1
49.9k
1%
L1, L2: SUMIDA CDRH125-270
P1: SILICONIX Si4953DY/FAIRCHILD NDS8947
R
SENSE1,
R
SENSE2
: DALE WSL-2010-.05
C
T1
300pF
Figure 1. High Efficiency Dual 3.3V/2.5V Regulator
U
12
9
8
10
U
U
+
0.22µF
P1B
L2
27µH
C
IN2
22µF
25V
×
2
R
SENSE2
0.05Ω
V
OUT2
2.5V/2A
1000pF
D2
MBRS320T3
R4
49.9k
1%
+
R3
49.9k
1%
C
OUT2
220µF
10V
×
2
100pF
1143 F01
1
LTC1143/LTC1143L
LTC1143L-ADJ
ABSOLUTE
MAXIMUM
RATINGS
Input Supply Voltage (Pins 5,13) ............... 16V to –0.3V
Continuous Output Current (Pins 4,12) ................ 50mA
Sense Voltages (Pins 1, 8, 9, 16)
V
IN
≥
12.7V .......................................... 13V to – 0.3V
V
IN
< 12.7V .............................. (V
IN
+ 0.3V) to – 0.3V
Shutdown Voltage
(LTC1143, LTC1143L, Pins 2, 10)...........7V to – 0.3V
V
FB
Current (LTC1143L-ADJ, Pins 2, 10) ............... 1mA
Operating Temperature Range
Ambient .................................................. 0°C to 70°C
Extended Commercial (Note 4) ........... –40°C to 85°C
Junction Temperature (Note 1) ............................. 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
SENSE
+
3
1
16
SENSE
–
3
ORDER PART
NUMBER
LTC1143CS
LTC1143LCS
SHUTDOWN 3 2
GND3 3
P-DRIVE 3 4
V
IN5
5
C
T5
6
I
TH5
7
SENSE
–
5
8
15 I
TH3
14 C
T3
13 V
IN3
12 P-DRIVE 5
11 GND5
10 SHUTDOWN 5
9
SENSE
+
5
S PACKAGE
16-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 95°C/W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
V
2
, V
10
I
2
, I
10
V
OUT
Feedback Voltage (LTC1143L-ADJ)
Feedback Current (LTC1143L-ADJ)
Regulated Output Voltage (LTC1143/LTC1143L)
3.3V Output
5V Output
Output Voltage Line Regulation
Output Voltage Load Regulation
LTC1143/LTC1143L
3.3V Output
5V Output
Output Ripple (Burst Mode)
I
5
, I
13
Input DC Supply Current (Note 2)
LTC1143:
Normal Mode
Sleep Mode
Shutdown
LTC1143L:
Normal Mode
Sleep Mode
Shutdown
LTC1143L-ADJ: Normal Mode
Sleep Mode
V
IN
= 9V
CONDITIONS
q
q
V
IN3,
V
IN5
= 9V, V
2
= V
10
= 0V
I
LOAD
= 700mA
I
LOAD
= 700mA
V
IN
= 7V to 12V, I
LOAD
= 50mA
V
2
= V
10
= 0V
5mA < I
LOAD
< 2.0A
5mA < I
LOAD
< 2.0A
I
LOAD
= 0A
V
2
= V
10
= 0V, 4V < V
IN
< 12V
V
2
= V
10
= 0V, 4V < V
IN3
< 12V, 6V < V
IN5
< 12V
V
2
= V
10
= 2.1V, 4V < V
IN
< 12V
V
2
= V
10
= 0V, 3.5V < V
IN
< 12V
V
2
= V
10
= 0V, 3.5V < V
IN3
< 12V, 6V < V
IN5
< 12V
V
2
= V
10
= 2.1V, 3.5V < V
IN
< 12V
3.5V < V
IN
< 12V
3.5V < V
IN
< 12V, V
OUT
≤
3.3V
∆V
OUT
2
U
U
W
W W
U
W
TOP VIEW
SENSE
+
1
1
16 SENSE
–
1
15 I
TH1
14 C
T1
13 V
IN1
12 P-DRIVE 2
11 GND2
10 V
FB2
9
SENSE
+
2
ORDER PART
NUMBER
LTC1143LCS-ADJ
V
FB1
2
GND1 3
P-DRIVE 1 4
V
IN2
5
C
T2
6
I
TH2
7
SENSE
–
2
8
S PACKAGE
16-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 95°C/W
T
A
= 25
°
C, V
IN
=
10V unless otherwise noted.
MIN
1.21
TYP
1.25
0.2
3.23
4.90
–40
3.33
5.05
0
MAX
1.29
1
3.43
5.20
40
UNITS
V
µA
V
V
mV
q
q
q
q
40
60
50
1.6
160
10
1.6
160
10
1.6
160
65
100
mV
mV
mV
P-P
2.1
230
20
2.1
230
20
2.1
230
mA
µA
µA
mA
µA
µA
mA
µA
LTC1143/LTC1143L
LTC1143L-ADJ
ELECTRICAL CHARACTERISTICS
SYMBOL
V
1
to V
16
,
V
8
to V
9
PARAMETER
Current Sense Threshold Voltage
LTC1143/LTC1143L
CONDITIONS
V
2
= V
10
= 0V
V
SENSE –
= V
OUT
+ 100mV (Forced)
V
SENSE –
= V
OUT
– 100mV (Forced)
V
SENSE–
= 5V, V
FB
= V
OUT
/4 + 25mV (Forced)
V
SENSE–
= 5V, V
FB
= V
OUT
/4 – 25mV (Forced)
T
A
= 25
°
C, V
IN
=
10V unless otherwise noted.
MIN
TYP
MAX
UNITS
q
q
130
130
0.5
LTC1143L-ADJ
V
2
, V
10
I
2
, I
10
I
6
, I
14
t
OFF
t
r
, t
f
Shutdown Pin Threshold
LTC1143/LTC1143L
Shutdown Pin Input Current
LTC1143/LTC1143L
C
T
Pin Discharge Current
Off-Time (Note 3)
Driver Output Transition Times
25
150
25
150
0.8
1.2
170
170
2
5
90
10
6
200
mV
mV
mV
mV
V
µA
µA
µA
µs
ns
0V < V
SHUTDOWN
= < 8V, V
IN3,
V
IN5
= 16V
V
OUT
in Regulation, V
SENSE-
= V
OUT
V
OUT
= 0V
C
T
= 390pF, I
LOAD
= 700mA
C
L
= 3000pF (Pins 4, 12), V
IN
= 6V
50
4
70
2
5
100
–40
°
C
≤
T
A
≤
85
°
C (Note 4), V
IN
= 10V unless otherwise noted.
V
2
, V
10
V
OUT
Feedback Voltage (LTC1143L-ADJ)
Regulated Output Voltage
LTC1143/LTC1143L
3.3V Output
5V Output
Input DC Supply Current (Note 2)
LTC1143:
Normal Mode
Sleep Mode
Shutdown
LTC1143L:
Normal Mode
Sleep Mode
Shutdown
LTC1143L-ADJ: Normal Mode
Sleep Mode
Current Sense Threshold Voltage
LTC1143/LTC1143L
V
IN
= 9V
V
IN3,
V
IN5
= 9V
I
LOAD
= 700mA
I
LOAD
= 700mA
V
2
= V
10
= 0V, 4V < V
IN
< 12V
V
2
= V
10
= 0V, 4V < V
IN3
< 12V, 6V < V
IN5
< 12V
V
2
= V
10
= 2.1V, 4V < V
IN
< 12V
V
2
= V
10
= 0V, 3.5V < V
IN
< 12V
V
2
= V
10
= 0V, 3.5V < V
IN3
< 12V, 6V < V
IN5
< 12V
V
2
= V
10
= 2.1V, 3.5V < V
IN
< 12V
3.5V < V
IN
< 12V
3.5V < V
IN
< 12V, V
OUT
≤
3.3V
V
2
= V
10
= 0V
V
SENSE –
= V
OUT
+ 100mV (Forced)
V
SENSE –
= V
OUT
– 100mV (Forced)
V
SENSE–
= 5V, V
FB
= V
OUT
/4 + 25mV (Forced)
V
SENSE–
= 5V, V
FB
= V
OUT
/4 – 25mV (Forced)
3.17
4.85
3.33
5.05
1.6
160
10
1.6
160
10
1.6
160
3.43
5.20
2.4
260
22
2.4
260
22
2.4
260
V
V
mA
µA
µA
mA
µA
µA
mA
µA
1.20
1.25
1.30
V
I
5
, I
13
V
1
to V
16
,
V
8
to V
9
125
125
0.55
LTC1143L-ADJ
V
2
, V
10
Shutdown Pin Threshold
LTC1143/LTC1143L
25
150
25
150
0.8
185
185
2
mV
mV
mV
mV
V
The
q
denotes specifications which apply over the specified temperature
range.
Note 1:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC1143 series: T
J
= T
A
+ (P
D
• 125°C/W)
Note 2:
This supply current is for one regulator block. Total supply
current is the sum of Pin 5 and Pin 13 currents. Dynamic supply current
is higher due to the gate charge being delivered at the switching
frequency. See Applications Information.
Note 3:
In applications where R
SENSE
is placed at ground potential, the
off-time increases approximately 40%.
Note 4:
The LTC1143 series is guaranteed to meet specified performance
from 0°C to 70°C and is designed, characterized and expected to meet
these extended temperature limits, but is not tested at –40°C to 85°C.
3
LTC1143/LTC1143L
LTC1143L-ADJ
TYPICAL PERFORMANCE CHARACTERISTICS
5V Output Efficiency
100
V
IN
= 6V
95
EFFICIENCY (%)
95
V
IN
= 5V
EFFICIENCY (%)
90
85
80
75
70
1
10
100
1000
LTC1143 G02
V
IN
= 10V
85
80
75
70
1
10
100
1000
LTC1143 G01
EFFICIENCY (%)
90
LOAD CURRENT (mA)
3.3V Efficiency vs Input Voltage
100
98
96
V
OUT
= 3.3V
40
30
20
EFFICIENCY (%)
94
∆V
OUT
(mV)
92
90
88
86
84
82
80
0
4
12
8
INPUT VOLTAGE (V)
16
LTC1143 G04
I
LOAD
= 1A
I
LOAD
= 100mA
0
–10
–20
–30
–40
0
4
12
8
INPUT VOLTAGE (V)
16
LTC1143 G05
∆V
OUT
(mV)
DC Supply Current
2.1
1.8
SUPPLY CURRENT (mA)
NOT INCLUDING
GATE CHARGE CURRENT
ACTIVE MODE
PINS 5, 13
NORMALIZED FREQUENCY
1.5
1.2
0.9
0.6
0.3
0
0
2
4
SUPPLY CURRENT (µA)
PER REGULATOR BLOCK
SLEEP MODE
8 10 12 14
6
INPUT VOLTAGE (V)
16
18
4
U W
LTC1143 • G07
3.3V Output Efficiency
100
100
98
96
94
92
90
88
86
84
82
80
5V Efficiency vs Input Voltage
V
OUT
= 5V
I
LOAD
= 1A
V
IN
= 10V
I
LOAD
= 100mA
0
4
LOAD CURRENT (mA)
12
8
INPUT VOLTAGE (V)
16
1143 G03
Line Regulation
20
V
OUT
= 5V
I
LOAD
= 1A
Load Regulation
R
SENSE
= 0.05Ω
0
–20
–40
–60
–80
–100
0
0.5
1.5
2.0
1.0
LOAD CURRENT (A)
2.5
LTC1143 G06
V
IN
= 6V
V
IN
= 12V
10
V
IN
= 6V
V
IN
= 12V
V
OUT
= 5V
V
OUT
= 3.3V
Supply Current in Shutdown
20
18
16
14
12
10
8
6
4
2
0
0
2
4
6
8 10 12 14
INPUT VOLTAGE (V)
16
18
0.2
0
1.6
Operating Frequency vs V
IN
– V
OUT
V
OUT
= 5V
1.4
0°C
1.2
25°C
1.0
0.8
0.6
0.4
70°C
PER LTC1143/LTC1143L
REGULATOR BLOCK
PINS 5, 13
V
SHUTDOWN
= 2V
0
2
4
6
8
10
12
(V
IN
– V
OUT
) VOLTAGE (V)
LTC1143 G08
LTC1143 G09
LTC1143/LTC1143L
LTC1143L-ADJ
TYPICAL PERFORMANCE CHARACTERISTICS
Gate Charge Supply Current
14
12
GATE CHARGE CURRENT (mA)
10
8
6
4
SENSE VOLTAGE (mV)
Q
P
= 100nC
OFF-TIME (µs)
Q
P
= 29nC
2
0
20
80
200
260
140
OPERATING FREQUENCY (kHz)
LTC1143 G10
PIN FUNCTIONS
LTC1143/LTC1143L
SENSE
+
3 (Pin 1):
The (+) Input to the 3.3V Section Current
Comparator. A built-in offset between Pins 1 and 16 in
conjunction with R
SENSE 3
sets the current trip threshold
for the 3.3V section.
SHUTDOWN 3 (Pin 2):
When grounded, the 3.3V section
operates normally. Pulling Pin 2 high holds the MOSFET
off and puts the 3.3V section in micropower shutdown
mode. Requires CMOS logic level signal with t
r
, t
f
< 1µs.
Do not “float” Pin 2.
GND3 (Pin 3):
3.3V Section Ground. Two independent
ground lines must be routed separately from other grounds
to: 1) the (–) terminal of the 3.3V section output capacitor
and 2) the cathode of the Schottky diode D1 and (–)
terminal of C
IN3
(see Figure 9).
P-DRIVE 3 (Pin 4):
High Current Drive for Top P-Channel
MOSFET, 3.3V Section. Voltage swing at this pin is from
V
IN3
to ground.
V
IN5
(Pin 5):
Supply Pin, 5V Section. Must be closely
decoupled to 5V power ground Pin 11.
C
T5
(Pin 6):
External capacitor C
T5
from Pin 6 to ground sets
the operating frequency for the 5V section. (The actual
frequency is also dependent upon the input voltage.)
I
TH5
(Pin 7):
Gain Amplifier Decoupling Point, 5V Section.
The 5V section current comparator threshold increases
with the Pin 7 voltage.
SENSE
–
5 (Pin 8):
Connects to internal resistive divider
which sets the output voltage for the 5V section. Pin 8 is
also the (–) input for the current comparator on the 5V
section.
SENSE
+
5 (Pin 9):
The (+) Input to the 5V Section Current
Comparator. A built-in offset between Pins 9 and 8 in
conjunction with R
SENSE 5
sets the current trip threshold
for the 5V section.
SHUTDOWN 5 (Pin 10):
When grounded, the 5V section
operates normally. Pulling Pin 10 high holds the 5V section
MOSFET off and puts the 5V section in micropower shut-
down mode. Requires CMOS logic level signal with t
r
, t
f
< 1µs.
Do not “float” Pin 10.
GND5 (Pin 11):
5V Section Ground. Two independent
ground lines must be routed separately from other grounds
to: 1) the (–) terminal of the 5V section output capacitor
and 2) the cathode of the Schottky diode D2 and (–)
terminal of C
IN5
(see Figure 9).
P-DRIVE 5 (Pin 12):
High Current Drive for Top P-Channel
MOSFET, 5V Section. Voltage swing at this pin is from
V
IN5
to ground.
U W
Off-Time vs V
OUT
80
70
60
50
40
30
20
10
0
0
V
OUT
= 3.3V
1
3
4
2
OUTPUT VOLTAGE (V)
5
LTC1143 G11
Current Sense Threshold Voltage
175
V
SENSE
= V
OUT
150
125
100
75
50
25
0
0
20
60
40
TEMPERATURE (°C)
80
100
LTC1143 G12
MAXIMUM
THRESHOLD
V
OUT
= 5V
MINIMUM
THRESHOLD
U
U
U
5
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