LTC1142/LTC1142L/LTC1142HV
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
FEATURES
s
s
s
DESCRIPTIO
s
s
s
s
s
s
s
Dual Outputs: 3.3V and 5V or User Programmable
Ultra-High Efficiency: Over 95% Possible
Current Mode Operation for Excellent Line and Load
Transient Response
High Efficiency Maintained over 3 Decades of
Output Current
Low Standby Current at Light Loads: 160µA/Output
Independent Micropower Shutdown: I
Q
< 40µA
Wide V
IN
Range: 3.5V to 20V
Very Low Dropout Operation: 100% Duty Cycle
Synchronous FET Switching for High Efficiency
Available in Standard 28-Pin SSOP
The LTC
®
1142/LTC1142L/LTC1142HV are dual synchro-
nous step-down switching regulator controllers featuring
automatic Burst Mode
TM
operation to maintain high efficien-
cies at low output currents. The devices are composed of two
separate regulator blocks, each driving a pair of external
complementary power MOSFETs, at switching frequencies
up to 250kHz, using a constant off-time current mode archi-
tecture providing constant ripple current in the inductor.
The operating current level for both regulators is user pro-
grammable via an external current sense resistor. Wide input
supply range allows operation from 3.5V* to 18V (20V
maximum). Constant off-time architecture provides low drop-
out regulation limited only by the R
DS(ON)
of the external
MOSFET and resistance of the inductor and current sense
resistor.
The LTC1142 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.
*For LTC1142L-ADJ only.
APPLICATI
s
s
s
s
S
Notebook and Palmtop Computers
Battery-Operated Digital Devices
Portable Instruments
DC Power Distribution Systems
TYPICAL APPLICATI
+
C
IN3
22µF
25V
×
2
V
IN
5.2V TO 18V
0.22µF
P-CH
Si9430DY
23
1
1000pF
28
SENSE
–
3
NDRIVE 3
PGND3 SGND3 C
T3
4
3
24
V
IN3
PDRIVE 3
SENSE
+
3
0V = NORMAL
>1.5V = SHUTDOWN
2
SHUTDOWN 3
16
SHUTDOWN 5
10
V
IN5
PDRIVE 5
SENSE
LTC1142HV
SENSE
–
5
0.22µF
P-CH
Si9430DY
9
L2
50µH
V
OUT3
3.3V/2A
R
SENSE3
0.05Ω
L1
50µH
+
5 15
14
20
N-CH
Si9410DY
D2
1N5818
D1
1N5818
6
N-CH
Si9410DY
NDRIVE 5
I
TH3
27
R
C3
1k
I
TH5
13
R
C5
1k
C
T5
11
SGND5 PGND5
17
18
+
C
OUT3
220µF
10V
×
2
25
R
SENSE3,
R
SENSE5
: SL-C1-1/2-1R050J
L1, L2: COILTRONICS CTX50-2-MP
PINS 5, 7, 8, 19, 21, 22: NC
C
C3
C
T3
C
T5
C
C5
560pF 3300pF 3300pF 390pF
1142 F01
NOTE: COMPONENTS OPTIMIZED FOR HIGHEST EFFICIENCY, NOT MINIMUM BOARD SPACE.
Figure 1. High Efficiency Dual 3.3V, 5V
U
+
C
IN5
22µF
25V
×
2
R
SENSE5
0.05Ω
V
OUT5
5V/2A
1000pF
UO
UO
+
C
OUT5
220µF
10V
×
2
1
LTC1142/LTC1142L/LTC1142HV
ABSOLUTE
AXI U
RATI GS
Extended Commercial
Temperature Range ........................... – 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
Input Supply Voltage (Pins 10, 24)
LTC1142, LTC1142L-ADJ ..................... 16V to – 0.3V
LTC1142HV, LTC1142HV-ADJ ............. 20V to – 0.3V
Continuous Output Current (Pins 6, 9, 20, 23) .... 50mA
Sense Voltages (Pins 1, 14, 15, 28).......... 13V to – 0.3V
Operating Ambient Temperature Range ...... 0°C to 70°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SENSE
+
3
SHUTDOWN 3
SGND 3
PGND 3
NC
NDRIVE 3
NC
NC
PDRIVE 5
1
2
3
4
5
6
7
8
9
LTC1142
28 SENSE
–
3
27 I
TH3
26 INT V
CC3
25 C
T3
24 V
IN3
23 PDRIVE 3
22 NC
21 NC
20 NDRIVE 5
19 NC
18 PGND5
17 SGND5
16 SHUTDOWN 5
15
SENSE
+
5
ORDER PART
NUMBER
LTC1142CG
LTC1142HVCG
V
IN5
10
C
T5
11
INT V
CC5
12
I
TH5
13
SENSE 5 14
–
G PACKAGE, 28-LEAD SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
2
, V
16
I
2
, I
16
V
OUT
PARAMETER
Feedback Voltage
Feedback Current
Regulated Output Voltage
3.3V Output
5V Output
Output Voltage Line Regulation
Output Voltage Load Regulation
3.3V Output
5V Output
Output Ripple (Burst Mode)
I
10
, I
24
Input DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
Input DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
T
A
= 25°C, V
10
= V
24
= 10V, V
SHUTDOWN
= 0V, unless otherwise noted.
MIN
1.21
q
q
q
CONDITIONS
LTC1142HV-ADJ, LTC1142L-ADJ : V
10
, V
24
= 9V
q
LTC1142HV-ADJ, LTC1142L-ADJ
LTC1142, LTC1142HV
I
LOAD
= 700mA, V
24
= 9V
I
LOAD
= 700mA, V
10
= 9V
V
10,
V
24
= 7V to 12V, I
LOAD
= 50mA
Figure 1 Circuit
5mA < I
LOAD
< 2A
5mA < I
LOAD
< 2A
I
LOAD
= 0A
LTC1142
4V < V
10
, V
24
< 12V
4V < V
24
< 12V, 6V < V
10
< 12V
V
SD1
= V
SD2
= 2.1V, 4V < V
10
, V
24
< 12V
LTC1142HV, LTC1142HV-ADJ
4V < V
10
, V
24
< 18V
4V < V
24
< 18V, 6V < V
10
< 18V
V
SD1
= V
SD2
= 2.1V, 4V < V
10
, V
24
< 18V
q
q
∆V
OUT
2
U
U
W
W W
U
W
TOP VIEW
SENSE
+
1 1
V
FB1
2
SHUTDOWN 1 3
SGND1 4
PGND1 5
NDRIVE 1 6
NC 7
NC 8
PDRIVE 2 9
V
IN2
10
C
T2
11
INT V
CC2
12
I
TH2
13
SENSE
–
2 14
LTC1142-ADJ
28 SENSE
–
1
27 I
TH1
26 INT V
CC1
25 C
T1
24 V
IN1
23 PDRIVE 1
22 NC
21 NC
20 NDRIVE 2
19 PGND2
18 SGND2
17 SHUTDOWN 2
16 V
FB2
15 SENSE
+
2
ORDER PART
NUMBER
LTC1142HVCG-ADJ
LTC1142LCG-ADJ
G PACKAGE, 28-LEAD SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
TYP
1.25
0.2
MAX
1.29
1
3.43
5.20
40
65
100
UNITS
V
µA
V
V
mV
mV
mV
mV
P-P
3.23
4.90
– 40
3.33
5.05
0
40
60
50
1.6
160
10
1.6
160
10
2.1
230
20
2.3
250
22
mA
µA
µA
mA
µA
µA
LTC1142/LTC1142L/LTC1142HV
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
Input DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
V
1
– V
28
V
15
– V
14
Current Sense Threshold Voltage
CONDITIONS
T
A
= 25°C, V
10
= V
24
= 10V, V
SHUTDOWN
= 0V, unless otherwise noted.
MIN
TYP
1.6
160
10
25
150
25
150
25
150
0.8
1.2
50
4
70
2
5
100
MAX
2.1
230
20
UNITS
mA
µA
µA
mV
mV
mV
mV
mV
mV
V
µA
µA
µA
µs
ns
LTC1142L-ADJ (Note 5)
3.5V < V
10
, V
24
< 12V
3.5V < V
10
, V
24
< 12V
V
SD1
= V
SD2
= 2.1V, 3.5V < V
10
, V
24
< 12V
LTC1142HV-ADJ, LTC1142L-ADJ
V
14
= V
28
= V
OUT
+ 100mV, V
2
= V
16
= V
REF
+ 25mV
V
14
= V
28
= V
OUT
– 100mV, V
2
= V
16
= V
REF
– 25mV
LTC1142, LTC1142HV
V
28
= V
OUT
+ 100mV (Forced)
V
28
= V
OUT
– 100mV (Forced)
LTC1142, LTC1142HV
V
14
= V
OUT
+ 100mV (Forced)
V
14
= V
OUT
– 100mV (Forced)
q
130
170
q
130
170
q
130
0.5
170
2
5
90
10
6
200
V
SHUTDOWN
I
SHUTDOWN
I
11
, I
24
t
OFF
t
r
, t
f
Shutdown Pin Threshold
Shutdown Pin Input Current
C
T
Pin Discharge Current
Off-Time (Note 3)
Driver Output Transition Times
0V < V
SHUTDOWN
< 8V, V
10
, V
24
= 16V
V
OUT
in Regulation, V
SENSE –
= V
OUT
V
OUT
= 0V
C
T
= 390pF, I
LOAD
= 700mA
C
L
= 3000pF (Pins 6, 9, 20, 23), V
10
, V
24
= 6V
– 40°C
≤
T
A
≤
85°C (Note 4), V
10
= V
24
= 10V, unless otherwise noted.
V
2
, V
16
I
2
, I
16
V
OUT
Feedback Voltage
Feedback Current
Regulated Output Voltage
3.3V Output
5V Output
Input DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
Input DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
Input DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
V
1
– V
28
V
15
– V
14
Current Sense Threshold Voltage
LTC1142HV-ADJ Only: V
10
, V
24
= 9V
LTC1142HV-ADJ Only
LTC1142, LTC1142HV
I
LOAD
= 700mA, V
24
= 9V
I
LOAD
= 700mA, V
10
= 9V
LTC1142
4V < V
10
, V
24
< 12V
4V < V
24
< 12V, 6V < V
10
< 12V
V
SHUTDOWN
= 2.1V, 4V < V
10
, V
24
< 12V
LTC1142HV-ADJ, LTC1142HV
4V < V
10
, V
24
< 18V
4V < V
24
< 18V, 6V < V
10
< 18V
V
SHUTDOWN
= 2.1V, 4V < V
10
, V
24
< 12V
LTC1142L-ADJ (Note 5)
3.5V < V
10
, V
24
< 12V
3.5V < V
10
, V
24
< 12V
V
SD1
= V
SD2
= 2.1V, 3.5V < V
10
, V
24
< 12V
LTC1142HV-ADJ, LTC1142L-ADJ
V
14
= V
28
= V
OUT
+ 100mV, V
2
= V
16
= V
REF
+ 25mV
V
14
= V
28
= V
OUT
– 100mV, V
2
= V
16
= V
REF
– 25mV
LTC1142, LTC1142HV
V
28
= V
OUT
+ 100mV (Forced)
V
28
= V
OUT
– 100mV (Forced)
LTC1142, LTC1142HV
V
14
= V
OUT
+ 100mV (Forced)
V
14
= V
OUT
– 100mV (Forced)
V
SHUTDOWN
t
OFF
Shutdown Pin Threshold
Off-Time (Note 3)
C
T
= 390pF, I
LOAD
= 700mA
3.17
4.85
1.21
1.25
0.2
3.33
5.05
1.6
160
10
1.6
160
10
1.6
160
10
25
150
25
150
25
150
0.8
5
1.29
1
3.40
5.20
2.4
260
22
2.6
280
24
2.4
260
22
V
µA
V
V
mA
µA
µA
mA
µA
µA
mA
µA
µA
mV
mV
mV
mV
mV
mV
V
µs
I
10
, I
24
130
170
125
175
125
0.55
3.8
175
2
6
3
LTC1142/LTC1142L/LTC1142HV
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
LTC1142CG: T
J
= T
A
+ (P
D
×
95°C/ W)
Note 2:
This current is for one regulator block. Total supply current is the
sum of Pins 10 and 24 currents. Dynamic supply current is higher due to
the gate charge being delivered at the switching frequency. See the
Applications Information section.
Note 3:
In applications where R
SENSE
is placed at ground potential, the off-
time increases approximately 40%.
Note 4:
The LTC1142/LTC1142HV-ADJ/LTC1142HV/LTC1142L-ADJ are
not tested and quality-assurance sampled at – 40°C to 85°C. These
specifications are guaranteed by design and/or correlation.
Note 5:
The LTC1142L-ADJ allows operation down to V
IN
= 3.5V.
TYPICAL PERFOR A CE CHARACTERISTICS
5V Output Efficiency
100
V
IN
= 6V
V
IN
= 5V
100
EFFICIENCY (%)
V
IN
= 10V
EFFICIENCY (%)
EFFICIENCY (%)
95
90
85
0.01
0.1
LOAD CURRENT (A)
3.3V Efficiency vs Input Voltage
100
98
96
EFFICIENCY (%)
FIGURE 1 CIRCUIT
V
OUT
= 3.3V
94
∆V
OUT
(mV)
92
90
88
86
84
82
80
0
4
I
LOAD
= 100mA
0
– 10
– 20
– 30
∆V
OUT
(mV)
I
LOAD
= 1A
12
8
INPUT VOLTAGE (V)
4
U W
1
2
1142 G01
3.3V Output Efficiency
100
98
96
94
92
90
88
86
84
82
85
0.01
5V Efficiency vs Input Voltage
FIGURE 1 CIRCUIT
V
OUT
= 5V
I
LOAD
= 1A
95
V
IN
= 10V
90
I
LOAD
= 100mA
80
0.1
LOAD CURRENT (A)
1
2
0
4
12
8
INPUT VOLTAGE (V)
16
20
1142 G03
1142 G02
Line Regulation
40
30
20
10
–20
– 40
– 60
– 80
– 100
0
4
12
8
INPUT VOLTAGE (V)
16
20
1142 G05
Load Regulation
20
FIGURE 1 CIRCUIT
R
SENSE
= 0.05Ω
V
IN
= 6V
V
IN
= 12V
FIGURE 1 CIRCUIT
I
LOAD
= 1A
0
V
IN
= 6V
V
IN
= 12V
V
OUT
= 5V
V
OUT
= 3.3V
0
0.5
1.5
2.0
1.0
LOAD CURRENT (A)
2.5
1142 G06
16
20
1142 G04
– 40
LTC1142/LTC1142L/LTC1142HV
TYPICAL PERFOR A CE CHARACTERISTICS
DC Supply Current
2.1
1.8
SUPPLY CURRENT (mA)
20
18
16
SUPPLY CURRENT (µA)
PER REGULATOR BLOCK
PINS 10, 24
V
SHUTDOWN
= 2V
NORMALIZED FREQUENCY
1.5
1.2
0.9
0.6
0.3
0
0
2
4
ACTIVE MODE
PER REGULATOR BLOCK
NOT INCLUDING
GATE CHARGE CURRENT
PINS 10, 24
SLEEP MODE
6
8 10 12 14
INPUT VOLTAGE (V)
Gate Charge Supply Current
28
24
80
70
GATE CHARGE CURRENT (mA)
20
16
12
8
Q
N
+ Q
P
= 100nC
OFF-TIME (µs)
SENSE VOLTAGE (mV)
Q
N
+ Q
P
= 50nC
4
0
20
80
200
260
140
OPERATING FREQUENCY (kHz)
1142 G10
PI FU CTIO S
LTC1142/LTC1142HV
SENSE
+
3 (Pin 1):
The (+) Input to the 3.3V Section
Current Comparator. A built-in offset between Pins 1 and
28 in conjunction with R
SENSE3
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 both MOSFETs
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.
SGND3 (Pin 3):
The 3.3V section small-signal ground
must be routed separately from other grounds to the (–)
terminal of the 3.3V section output capacitor.
PGND3 (Pin 4):
The 3.3V section driver power ground
connects to source of N-channel MOSFET and the (–)
terminal of the 3.3V section input capacitor.
NC (Pin 5):
No Connection.
NDRIVE 3 (Pin 6):
High Current Drive for Bottom N-Channel
MOSFET, 3.3V Section. Voltage swing at Pin 6 is from
ground to V
IN3
.
U W
16
1142 G07
Supply Current in Shutdown
1.6
1.4
Operating Frequency vs
V
IN
– V
OUT
V
OUT
= 5V
0°C
1.2
1.0
0.8
0.6
0.4
0.2
0
25°C
70°C
14
12
10
8
6
4
2
0
18
0
2
4
6
8 10 12 14
INPUT VOLTAGE (V)
16
18
0
2
4
6
8
10
12
1142 G09
V
IN
– V
OUT
VOLTAGE (V)
1142 G08
Off-Time vs Output Voltage
175
Current Sense Threshold Voltage
150
125
100
75
50
25
0
MINIMUM
THRESHOLD
MAXIMUM
THRESHOLD
V
SENSE
= V
OUT
60
50
40
30
20
10
0
0
V
OUT
= 3.3V
1
3
4
2
OUTPUT VOLTAGE (V)
5
1142 G11
V
OUT
= 5V
0
20
60
40
TEMPERATURE (°C)
80
100
1142 G12
U
U
U
5
