FEATURES
LTC1142/LTC1142L/LTC1142HV
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
U
DESCRIPTIO
■
Dual Outputs: 3.3V and 5V or User Programmable
■
Ultrahigh 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
■
Wide VIN Range: 3.5V to 20V
■
Very Low Dropout Operation: 100% Duty Cycle
■
Synchronous FET Switching for High Efficiency
■
Available in Standard 28-Pin SSOP
< 40µA
Q
U
APPLICATIO S
■
Notebook and Palmtop Computers
■
Battery-Operated Digital Devices
■
Portable Instruments
■
DC Power Distribution Systems
The LTC®1142/LTC1142L/LTC1142HV are dual synchronous step-down switching regulator controllers featuring
automatic Burst ModeTM operation to maintain high efficiencies 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 architecture providing constant ripple current in the inductor.
The operating current level for both regulators is user programmable 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 dropout regulation limited only by the R
of the external
DS(ON)
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.
TYPICAL APPLICATIO
C
IN3
+
22µF
25V
× 2
P-CH
Si9430DY
V
OUT3
3.3V/2A
R
SENSE3
0.05Ω
+
L1
50µH
1000pF
D1
MBRS130L
C
OUT3
220µF
10V
× 2
R
SENSE3, RSENSE5
L1, L2: COILTRONICS CTX50-2-MP
PINS 5, 7, 8, 19, 21, 22: NC
NOTE: COMPONENTS OPTIMIZED FOR HIGHEST EFFICIENCY, NOT MINIMUM BOARD SPACE.
N-CH
Si9410DY
: DALE WSL-2010-.05
U
V
IN
5.2V TO 18V
0.22µF
24 16 10
V
IN3
23
PDRIVE 3
1
+
SENSE
3
–
SENSE
28
3
NDRIVE 3
6
PGND3 SGND3 C
4 3 25 27 13 11 17 18
Figure 1. High Efficiency Dual 3.3V, 5V Supply
0V = NORMAL
>1.5V = SHDN
2
SHDN3
LTC1142HV
T3ITH3ITH5
C
C
T3
3300pF
560pF
SHDN5
C
SGND5
T5
R
R
C5
C3
1k
1k
C
C
C5
3300pF
T5
390pF
C3
V
IN5
PDRIVE 5
SENSE
SENSE
NDRIVE 5
PGND5
C
IN5
+
0.22µF
P-CH
Si9430DY
9
15
+
5
–
1000pF
5
14
20
N-CH
Si9410DY
22µF
25V
× 2
L2
50µH
D2
MBRS130L
1142 F01
R
SENSE5
0.05Ω
V
OUT5
5V/2A
C
OUT5
+
220µF
10V
× 2
1
LTC1142/LTC1142L/LTC1142HV
1
2
3
4
5
6
7
8
9
10
11
12
13
14
TOP VIEW
G PACKAGE
28-LEAD PLASTIC SSOP
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SENSE
+
1
V
FB1
SHDN1
SGND1
PGND1
NDRIVE 1
NC
NC
PDRIVE 2
V
IN2
C
T2
INTV
CC2
I
TH2
SENSE–2
SENSE
–
1
I
TH1
INTV
CC1
C
T1
V
IN1
PDRIVE 1
NC
NC
NDRIVE 2
PGND2
SGND2
SHDN2
V
FB2
SENSE+2
WW
W
ABSOLUTE AXI U RATI GS
U
(Note 1)
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)
VIN > 13V.............................................. 13V to – 0.3V
VIN < 13V.................................. (VIN + 0.3V) to –0.3V
UUW
PACKAGE/ORDER I FOR ATIO
TOP VIEW
+
1
SENSE
3
2
SHDN3
3
SGND3
4
PGND3
5
NC
6
NDRIVE 3
7
NC
8
NC
9
PDRIVE 5
10
V
IN5
11
C
T5
12
INTV
CC5
13
I
TH5
14
SENSE–5
G PACKAGE
28-LEAD PLASTIC SSOP
T
= 125°C, θJA = 95°C/W T
JMAX
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SENSE
I
TH3
INTV
CC3
C
T3
V
IN3
PDRIVE 3
NC
NC
NDRIVE 5
NC
PGND5
SGND5
SHDN5
SENSE
–
3
+
5
Consult factory for Industrial and Military grade parts.
ORDER PART
NUMBER
LTC1142CG
LTC1142HVCG
Operating Ambient Temperature Range ...... 0°C to 70°C
Extended Commercial
Temperature Range ........................... –40°C to 85°C
Junction Temperature (Note 2)............................ 125°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1142HVCG-ADJ
LTC1142LCG-ADJ
= 125°C, θJA = 95°C/W
JMAX
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at T
The ● denotes the specifications which apply over the full operating
= 25°C. V
A
= V
10
= 10V, V
24
= 0V unless otherwise noted.
SHDN
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V2, V
16
I2, I
16
V
OUT
∆V
OUT
I10, I
24
2
Feedback Voltage LTC1142HV-ADJ, LTC1142L-ADJ : V10, V24 = 9V ● 1.21 1.25 1.29 V
Feedback Current LTC1142HV-ADJ, LTC1142L-ADJ ● 0.2 1 µA
Regulated Output Voltage LTC1142, LTC1142HV
3.3V Output I
5V Output I
Output Voltage Line Regulation V
Output Voltage Load Regulation Figure 1 Circuit
3.3V Output 5mA < I
5V Output 5mA < I
Output Ripple (Burst Mode) I
Input DC Supply Current (Note 3) LTC1142
Normal Mode 4V < V
Sleep Mode 4V < V24 < 12V, 6V < V
Shutdown V
= 700mA, V24 = 9V ● 3.23 3.33 3.43 V
LOAD
= 700mA, V10 = 9V ● 4.90 5.05 5.20 V
LOAD
= 7V to 12V, I
10, V24
< 2A ● 40 65 mV
LOAD
< 2A ● 60 100 mV
LOAD
= 0A 50 mV
LOAD
, V
< 12V 1.6 2.1 mA
10
24
= V
SD1
= 2.1V, 4V < V10, V
SD2
= 50mA – 40 0 40 mV
LOAD
< 12V 160 230 µA
10
< 12V 10 20 µA
24
P-P
LTC1142/LTC1142L/LTC1142HV
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at T
The ● denotes the specifications which apply over the full operating
= 25°C. V
A
= V
10
= 10V, V
24
= 0V unless otherwise noted.
SHDN
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Input DC Supply Current (Note 3) LTC1142HV, LTC1142HV-ADJ
Normal Mode 4V < V
Sleep Mode 4V < V24 < 18V, 6V < V
Shutdown V
SD1
, V
< 18V 1.6 2.3 mA
10
24
= V
= 2.1V, 4V < V10, V
SD2
< 18V 160 250 µA
10
< 18V 10 22 µA
24
Input DC Supply Current (Note 3) LTC1142L-ADJ (Note 6)
V1 – V
V
– V
15
Normal Mode 3.5V < V
Sleep Mode 3.5V < V
Shutdown V
Current Sense Threshold Voltage LTC1142HV-ADJ, LTC1142L-ADJ
28
14
SD1
V
14
V
14
, V24 < 12V 1.6 2.1 mA
10
, V
< 12V 160 230 µA
10
24
= V
= 2.1V, 3.5V < V10, V
SD2
= V28 = V
= V28 = V
OUT
OUT
+ 100mV, V2 = V16 = V
– 100mV, V2 = V16 = V
< 12V 10 20 µA
24
+ 25mV 25 mV
REF
– 25mV ● 130 150 170 mV
REF
LTC1142, LTC1142HV
V28 = V
V
28
+ 100mV (Forced) 25 mV
OUT
= V
– 100mV (Forced) ● 130 150 170 mV
OUT
LTC1142, LTC1142HV
V
= V
+ 100mV (Forced) 25 mV
OUT
= V
– 100mV (Forced) ● 130 150 170 mV
OUT
< 8V, V10, V
SHDN
LOAD
= 16V 1.2 5 µA
24
–
SENSE
= V
OUT
50 70 90 µA
= 700mA 4 5 6 µs
V
SHDN
I
SHDN
I11, I
t
OFF
tr, t
14
V
14
Shutdown Pin Threshold 0.5 0.8 2 V
Shutdown Pin Input Current 0V < V
24
CT Pin Discharge Current V
in Regulation, V
OUT
V
= 0V 2 10 µA
OUT
Off-Time (Note 4) CT = 390pF, I
f
Driver Output Transition Times CL = 3000pF (Pins 6, 9, 20, 23), V10, V24 = 6V 100 200 ns
–40°C ≤ TA ≤ 85°C (Note 5), V
10
= V
= 10V, unless otherwise noted.
24
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V2, V
I2, I
V
OUT
I10, I
16
16
24
Feedback Voltage LTC1142HV-ADJ Only: V10, V24 = 9V 1.21 1.25 1.29 V
Feedback Current LTC1142HV-ADJ Only 0.2 1 µA
Regulated Output Voltage LTC1142, LTC1142HV
3.3V Output I
5V Output I
= 700mA, V24 = 9V 3.17 3.33 3.43 V
LOAD
= 700mA, V10 = 9V 4.85 5.05 5.20 V
LOAD
Input DC Supply Current (Note 3) LTC1142
Normal Mode 4V < V10, V
Sleep Mode 4V < V
Shutdown V
SHDN
< 12V 1.6 2.4 mA
24
< 12V, 6V < V
24
= 2.1V, 4V < V10, V
< 12V 160 260 µA
10
< 12V 10 22 µA
24
Input DC Supply Current (Note 3) LTC1142HV-ADJ, LTC1142HV
Normal Mode 4V < V10, V
Sleep Mode 4V < V
Shutdown V
SHDN
< 18V 1.6 2.6 mA
24
< 18V, 6V < V
24
= 2.1V, 4V < V10, V
< 18V 160 280 µA
10
< 12V 10 24 µA
24
Input DC Supply Current (Note 3) LTC1142L-ADJ (Note 6)
, V24 < 12V 1.6 2.4 mA
10
, V
< 12V 160 260 µA
10
24
= V
= 2.1V, 3.5V < V10, V
SD2
= V28 = V
= V28 = V
OUT
OUT
+ 100mV, V2 = V16 = V
– 100mV, V2 = V16 = V
< 12V 10 22 µA
24
+ 25mV 25 mV
REF
– 25mV 125 150 175 mV
REF
V1 – V
V
– V
15
Normal Mode 3.5V < V
Sleep Mode 3.5V < V
Shutdown V
Current Sense Threshold Voltage LTC1142HV-ADJ, LTC1142L-ADJ
28
14
SD1
V
14
V
14
LTC1142, LTC1142HV
V
= V
28
V28 = V
+ 100mV (Forced) 25 mV
OUT
– 100mV (Forced) 125 150 175 mV
OUT
3
LTC1142/LTC1142L/LTC1142HV
ELECTRICAL CHARACTERISTICS
–40°C ≤ TA ≤ 85°C (Note 5), V
10
= V
= 10V, unless otherwise noted.
24
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
LTC1142, LTC1142HV
V
= V
14
V
14
V
t
OFF
SHDN
Shutdown Pin Threshold 0.55 0.8 2 V
Off-Time (Note 4) CT = 390pF, I
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: T
dissipation P
is calculated from the ambient temperature TA and power
J
according to the following formula:
D
LTC1142CG: T
= TA + (P
J
× 95°C/W)
D
Note 3: 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
+ 100mV (Forced) 25 mV
OUT
= V
– 100mV (Forced) 125 150 175 mV
OUT
= 700mA 3.8 5 6 µs
LOAD
Note 4: In applications where R
is placed at ground potential, the off-
SENSE
time increases approximately 40%.
Note 5: The LTC1142/LTC1142L/LTC1142HV are guaranteed to meet
specified performance from 0°C to 70°C and are designed, characterized
and expected to meet these extended temperature limits, but are not tested
at –40°C and 85°C. Guaranteed I-grade parts are available, consult the
factory.
Note 6: The LTC1142L-ADJ allows operation down to V
= 3.5V.
IN
Applications Information section.
UW
TYPICAL PERFOR A CE CHARACTERISTICS
5V Output Efficiency 3.3V Output Efficiency 5V Efficiency vs Input Voltage
100
95
EFFICIENCY (%)
90
85
0.01
VIN = 6V
VIN = 10V
0.1 1
LOAD CURRENT (A)
1142 G01
2
100
95
EFFICIENCY (%)
90
85
0.01
VIN = 5V
VIN = 10V
0.1 1
LOAD CURRENT (A)
2
1142 G02
100
98
96
94
92
90
88
EFFICIENCY (%)
86
84
82
80
0
I
= 100mA
LOAD
4
8
INPUT VOLTAGE (V)
FIGURE 1 CIRCUIT
V
= 5V
OUT
I
= 1A
LOAD
12
16
20
1142 G03
3.3V Efficiency vs Input Voltage Load RegulationLine Regulation
(mV)
OUT
∆V
–10
–20
–30
–40
40
30
20
10
0
0
100
98
96
94
92
90
88
EFFICIENCY (%)
86
84
82
80
0
I
= 100mA
LOAD
4
INPUT VOLTAGE (V)
FIGURE 1 CIRCUIT
V
8
OUT
I
LOAD
12
= 3.3V
= 1A
16
20
1142 G04
4
FIGURE 1 CIRCUIT
= 1A
I
LOAD
4
8
INPUT VOLTAGE (V)
20
0
–20
(mV)
–40
OUT
∆V
–60
–80
12
16
20
1142 G05
–100
0
VIN = 6V
V
OUT
V
OUT
0.5
LOAD CURRENT (A)
VIN = 6V
= 5V
= 3.3V
1.0
FIGURE 1 CIRCUIT
= 0.05Ω
R
SENSE
VIN = 12V
VIN = 12V
1.5
2.0
2.5
1142 G06
LTC1142/LTC1142L/LTC1142HV
UW
TYPICAL PERFOR A CE CHARACTERISTICS
DC Supply Current
2.1
1.8
1.5
1.2
PER REGULATOR BLOCK
NOT INCLUDING
0.9
GATE CHARGE CURRENT
PINS 10, 24
0.6
SUPPLY CURRENT (mA)
0.3
0
0
4
2
6
INPUT VOLTAGE (V)
ACTIVE MODE
SLEEP MODE
12 16
10
8
14
18
1142 G07
Supply Current in Shutdown
20
PER REGULATOR BLOCK
18
PINS 10, 24
V
16
14
12
10
8
6
SUPPLY CURRENT (µA)
4
2
0
0
SHUTDOWN
2
4
= 2V
6
8
INPUT VOLTAGE (V)
10
14
12 16
1142 G08
1.6
1.4
1.2
1.0
0.8
0.6
0.4
NORMALIZED FREQUENCY
0.2
18
Operating Frequency vs
VIN – V
OUT
V
= 5V
OUT
0°C
25°C
0
0
2
4
VIN – V
68
VOLTAGE (V)
OUT
70°C
10
12
1142 G09
Gate Charge Supply Current
28
24
20
16
12
8
GATE CHARGE CURRENT (mA)
4
0
20
QN + QP = 100nC
QN + QP = 50nC
80 260200
OPERATING FREQUENCY (kHz)
140
1142 G10
Off-Time vs Output Voltage
80
70
60
50
40
30
OFF-TIME (µs)
20
10
V
= 3.3V
0
OUT
1
0
2
OUTPUT VOLTAGE (V)
UUU
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
threshold for the 3.3V section.
SHDN3 (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 tr, t
“float” Pin 2.
sets the current trip
SENSE3
< 1µs. Do not
f
Current Sense Threshold Voltage
V
= V
SENSE
OUT
V
= 5V
OUT
3
4
5
1142 G11
175
150
125
100
75
50
SENSE VOLTAGE (mV)
25
0
20
0
40
TEMPERATURE (°C)
MAXIMUM
THRESHOLD
MINIMUM
THRESHOLD
60
80
100
1142 G12
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
.
5
LTC1142/LTC1142L/LTC1142HV
UUU
PI FU CTIO S
NC (Pins 7, 8): No Connection.
PDRIVE 5 (Pin 9): High Current Drive for Top P-Channel
MOSFET, 5V Section. Voltage swing at this pin is from V
to ground.
V
(Pin 10): Supply pin, 5V section, must be closely
IN5
decoupled to 5V power ground Pin 18.
CT5 (Pin 11): External capacitor CT5 from Pin 11 to ground
sets the operating frequency for the 5V section. (The actual
frequency is also dependent upon the input voltage.)
INTV
section, nominally 3.3V, can be decoupled to signal ground,
Pin 17. Do not externally load this pin.
I
TH5
tion. The 5V section current comparator threshold increases with the Pin 13 voltage.
SENSE–5 (Pin 14): Connects to internal resistive divider
which sets the output voltage for the 5V section. Pin 14 is
also the (–) input for the current comparator on the
5V section.
(Pin 12) : Internal supply voltage for the 5V
CC5
(Pin 13): Gain Amplifier Decoupling Point, 5V Sec-
IN5
NC (Pins 21, 22): No Connection.
PDRIVE 3 (Pin 23): High Current Drive for Top P-Channel
MOSFET, 3.3V Section. Voltage swing at this pin is from
V
to ground.
IN3
V
(Pin 24): Supply pin, 3.3V section, must be closely
IN3
decoupled to 3.3V power ground, Pin 4.
C
(Pin 25): External capacitor CT3 from Pin 25 to ground
T3
sets the operating frequency for the 3.3V section. (The
actual frequency is also dependent upon the input voltage.)
INTV
section, nominally 3.3V, can be decoupled to signal ground,
Pin 3. Do not externally load this pin.
I
TH3
Section. The 3.3V section current comparator threshold
increases with the Pin 27 voltage.
SENSE–3 (Pin 28): Connects to internal resistive divider
which sets the output voltage for the 3.3V section. Pin 28
is also the (–) input for the current comparator on the
3.3V section.
(Pin 26): Internal supply voltage for the 3.3V
CC3
(Pin 27): Gain Amplifier Decoupling Point, 3.3V
SENSE+5 (Pin 15): The (+) Input to the 5V Section Current
Comparator. A built-in offset between Pins 15 and 14 in
conjunction with R
for the 5V section.
SHDN5 (Pin 16): When grounded, the 5V section operates
normally. Pulling Pin 16 high holds both MOSFETs off and
puts the 5V section in micropower shutdown mode.
Requires CMOS logic signal with tr, t
Pin 16.
SGND5 (Pin 17): The 5V section small-signal ground must
be routed separately from other grounds to the (–) terminal of the 5V section output capacitor.
PGND5 (Pin 18): The 5V section driver power ground
connects to source of N-channel MOSFET and the (–)
terminal of the 5V section input capacitor.
NC (Pin 19): No Connection.
NDRIVE 5 (Pin 20): High Current Drive for Bottom
N-Channel MOSFET, 5V Section. Voltage swing at Pin 20
is from ground to V
sets the current trip threshold
SENSE5
< 1µs. Do not “float”
f
.
IN5
LTC1142HV-ADJ/LTC1142L-ADJ
SENSE+1 (Pin 1): The (+) Input to the Section 1 Current
Comparator. A built-in offset between Pins 1 and 28 in
conjunction with R
for this section.
V
(Pin 2): This pin serves as the feedback pin from an
FB1
external resistive divider used to set the output voltage for
section 1.
SHDN1 (Pin 3): When grounded, the section 1 regulator
operates normally. Pulling Pin 3 high holds both MOSFETs
off and puts this section in micropower shutdown mode.
Requires CMOS logic signal with tr, t
Pin 3.
SGND1 (Pin 4): The section 1 small-signal ground must
be routed separately from other grounds to the (–) terminal of the section 1 output capacitor.
PGND1 (Pin 5): The section 1 driver power ground connects to source of N-channel MOSFET and the (–) terminal
of the section 1 input capacitor.
sets the current trip threshold
SENSE1
< 1µs. Do not “float”
f
6
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