LTC1267
LTC1267-ADJ/LTC1267-ADJ5
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
FEATURES
s
s
s
s
s
DESCRIPTIO
s
s
s
s
s
Dual Outputs: 3.3V and 5V, Two Adjustables or
Adjustable and 5V
Wide V
IN
Range: 4V to 40V
Ultra-High Efficiency: Up to 95%
Low Supply Current in Shutdown: 20
µ
A
Current Mode Operation for Excellent Line and Load
Transient Response
High Efficiency Maintained Over a Wide Output
Current Range
Independent Micropower Shutdown
Very Low Dropout Operation: 100% Duty Cycle
Synchronous FET Switching for High Efficiency
Available in Standard 28-Pin SSOP
The LTC
®
1267 series are dual synchronous step-down
switching regulator controllers featuring automatic Burst
Mode
TM
operation to maintain high efficiencies at low
output currents. The LTC1267 is composed of two sepa-
rate regulator blocks, each driving a pair of external comple-
mentary power MOSFETs at switching frequencies up to
400kHz. The LTC1267 uses a constant off-time current-
mode architecture to provide constant ripple current in the
inductor and provide excellent line and load transient
response.
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 voltage. The output current level is
user-programmable via an external current sense resistor.
The LTC1267 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.
APPLICATI
s
s
s
s
S
Notebook and Palmtop Computers
Battery-Operated Digital Devices
Portable Instruments
DC Power Distribution Systems
TYPICAL APPLICATI
+
C
IN3
100µF
50V
V
IN
5.4V to 25V
+
3.3µF
P-CH
Si9435DY
1N4148
8
4
5
14
1000pF
13
12
SENSE
–
3
SHDN3
NGATE 3
V
CC3
PGATE 3
PDRIVE 3
SENSE
+
3
0.15µF
3
CAP3
1
V
CC
2
V
IN
0.15µF
1N4148
27
26
28
21
PGATE 5
PDRIVE 5
SENSE
+
5
LTC1267
SENSE
–
5
SHDN5
NGATE 5
I
TH3
10
I
TH5
15
C
T5
16
SGND5 PGND5
20
22
17
19
23
N-CH
Si9410DY
25
24
18
1000pF
0.1µF
P-CH
Si9435DY
MSHDN CAP5 EXT V
CC
V
CC5
V
OUT3
3.3V
2A
R
SENSE3
0.05Ω
L3
20µH
0.1µF
D3
MBRS140T3
6
N-CH
Si9410DY
+
C
OUT3
220µF
10V
×
2
PGND3 SGND3 C
T3
7
11
9
C
C3
C
C5
C
T5
C
T3
270pF 3300pF 3300pF 270pF
R
SENSE3
: KRL SL-1R050J
L3: COILTRONICS CTX20-4
R
C3
1k
R
C5
1k
R
SENSE5
: KRL SL-1R050J
L5: COILTRONICS CTX33-4
LTC1267 • F01
SHDN3, SHDN5, MSHDN
0V = NORMAL, >2V = SHDN
Figure 1. High Efficiency Dual 3.3V, 5V
U
+
+
3.3µF
C
IN5
100µF
50V
L5
33µH
R
SENSE5
0.05Ω
V
OUT5
5V
2A
D5
MBRS140T3
UO
UO
+
C
OUT5
220µF
10V
×
2
1
LTC1267
LTC1267-ADJ/LTC1267-ADJ5
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
CC
1
V
IN
2
CAP3 3
PGATE 3 4
PDRIVE 3 5
NGATE 3 6
PGND3 7
V
CC3
8
C
T3
9
I
TH3
10
SGND3 11
SHDN3 12
SENSE
–
3 13
SENSE
+
3 14
28 EXT V
CC
27 MSHDN
26 CAP5
25 PGATE 5
24 PDRIVE 5
23 NGATE 5
22 PGND5
21 V
CC5
20 SGND5
19 SHDN5
18 SENSE
+
5
17 SENSE
–
5
16 C
T5
15 I
TH5
Input Supply Voltage (Pin 2)..................... – 0.3V to 40V
V
CC
Output Current (Pin 1) .................................. 50mA
EXT V
CC
Input Voltage (Pin 28) .............................. 10V
Continuous Output Current (Pins 5, 6, 23, 24) .... 50mA
Sense Voltages
LTC1267 (Pins 13, 14, 17, 18) ............. V
CC
to – 0.3V
LTC1267-ADJ (Pins 12, 13, 17, 18) ..... V
CC
to – 0.3V
LTC1267-ADJ5 (Pins 12, 13, 17, 18) ... V
CC
to – 0.3V
Shutdown Voltages
LTC1267 (Pins 12, 19, 27) ................................... 7V
LTC1267-ADJ (Pins 11, 27) ................................. 7V
LTC1267-ADJ5 (Pins 11, 19, 27) ......................... 7V
Operating Ambient Temperature Range ...... 0°C to 70°C
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
TOP VIEW
V
CC
1
V
IN
2
CAP1 3
PGATE 1 4
PDRIVE 1 5
NGATE 1 6
V
CC1
7
C
T1
8
I
TH1
9
SGND1 10
SHDN1 11
SENSE
–
1 12
SENSE
+
1 13
V
FB1
14
28 EXT V
CC
27 MSHDN
26 CAP2
25 PGATE 2
24 PDRIVE 2
23 NGATE 2
22 PGND
21 V
CC2
20 SGND2
19 V
FB2
18
SENSE
+
2
17 SENSE
–
2
16 C
T2
15 I
TH2
ORDER PART
NUMBER
LTC1267CG
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
ORDER PART
NUMBER
LTC1267CG-ADJ
TOP VIEW
V
CC
1
V
IN
2
CAP1 3
PGATE 1 4
PDRIVE 1 5
NGATE 1 6
V
CC1
7
C
T1
8
I
TH1
9
SGND1 10
SHDN1 11
SENSE
–
1 12
SENSE
+
1 13
V
FB1
14
28 EXT V
CC
27 MSHDN
26 CAP5
25 PGATE 5
24 PDRIVE 5
23 NGATE 5
22 PGND
21 V
CC5
20 SGND5
19 SHDN5
18 SENSE
+
5
17 SENSE
–
5
16 C
T5
15 I
TH5
ORDER PART
NUMBER
LTC1267CG-ADJ5
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 95°C/W
Consult factory for Industrial and Military grade parts.
The LTC1267 demo circuit board is now available. Consult factory.
2
U
W
U
U
W W
W
LTC1267
LTC1267-ADJ/LTC1267-ADJ5
ELECTRICAL CHARACTERISTICS
T
A
= 25°C, V
IN
= 12V, V
MSHDN,
V
SHDN1,3,5
= 0V (Note 2), unless otherwise noted.
SYMBOL
V
FB1
,
2
I
FB1
,
2
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
Burst Mode Output Ripple
V
CC
V
IN
– V
CC
I
EXTVCC
I
IN
Internal Regulator Voltage
V
CC
Dropout Voltage
EXT V
CC
Pin Current (Note 3)
V
IN
Pin Current (Note 3)
Normal
Shutdown
V
EXTVCC
–
V
CC
V
PGATE
–
V
IN
EXT V
CC
Switch Drop
PGate to Source Voltage (Off)
CONDITIONS
LTC1267-ADJ, LTC1267-ADJ5: V
IN
= 9V
LTC1267-ADJ, LTC1267-ADJ5
LTC1267: V
IN
= 9V, I
LOAD
= 700mA
LTC1267, LTC1267-ADJ5: V
IN
= 9V, I
LOAD
= 700mA
V
IN
= 9V to 40V
Figure 1 Circuit
5mA < I
LOAD
< 2.0A
5mA < I
LOAD
< 2.0A
I
LOAD
= 0A
V
IN
= 12V to 40V, EXT V
CC
= 0V, I
CC
= 10mA
V
IN
= 4V, EXT V
CC
= Open, I
CC
= 10mA
EXT V
CC
= 5V, Sleep Mode
V
IN
= 12V, EXT V
CC
= 5V
V
IN
= 40V, EXT V
CC
= 5V
V
IN
= 12V, V
MSHDN
= 2V
V
IN
= 40V, V
MSHDN
= 2V
V
IN
= 12V, EXT V
CC
= 5V, I
SWITCH
= 10mA
V
IN
= 12V
V
IN
= 40V
LTC1267-ADJ, LTC1267-ADJ5
V
SENSE –1, 2
= 5.1V, V
FB1, 2
= V
OUT
/4 + 25mV (Forced)
V
SENSE – 1, 2
= 4.9V, V
FB1, 2
= V
OUT
/4 – 25mV (Forced)
LTC1267
V
SENSE – 3, 5
= V
OUT
+ 100mV (Forced)
V
SENSE – 3, 5
= V
OUT
– 100mV (Forced)
– 0.2
– 0.2
q
q
q
q
q
q
q
MIN
1.21
TYP
1.25
0.2
MAX
1.29
1
3.43
5.20
40
65
100
4.75
300
UNITS
V
µA
V
V
mV
mV
mV
mV
P-P
V
mV
µA
µA
µA
µA
µA
3.23
4.90
– 40
3.33
5.05
0
40
60
50
∆V
OUT
4.25
4.5
200
360
320
550
15
25
200
0
0
25
160
25
160
1.4
0.8
12
70
2
5
100
300
mV
V
V
mV
mV
mV
mV
V
V
µA
µA
µA
µs
ns
V
SENSE +1, 2
– Current Sense Threshold Voltage
V
SENSE –1, 2
V
SENSE + 3, 5
– Current Sense Threshold Voltage
V
SENSE –3, 5
V
SHDN
Shutdown Threshold
MSHDN
SHDN1, 3, 5
MSHDN Input Current
C
T
Pin Discharge Current
Off-Time (Note 4)
Driver Output Transition Times
q
135
180
q
135
0.8
0.6
180
2.0
2.0
20
90
10
6
200
I
MSHDN
I
CT
t
OFF
t
r
, t
f
V
MSHDN
= 5V
V
OUT
in Regulation
V
OUT
= 0V
C
T
= 390pF, I
LOAD
= 700mA, V
IN
= 10V
C
L
= 3000pF (PDrive and NGate Pins), V
IN
= 6V
50
4
3
LTC1267
LTC1267-ADJ/LTC1267-ADJ5
ELECTRICAL CHARACTERISTICS
SYMBOL
V
FB1
,
2
V
OUT
PARAMETER
Feedback Voltage
Regulated Output Voltage
3.3V Output
5V Output
V
IN
Pin Current (Note 3)
Normal
Shutdown
I
EXTVCC
V
CC
V
SENSE +
–
V
SENSE –
V
MSHDN
t
OFF
EXT V
CC
Pin Current (Note 3)
Internal Regulator Voltage
Current Sense Threshold Voltage
Shutdown Threshold MSHDN
Off-Time (Note 4)
CONDITIONS
– 40°C
≤
T
A
≤
85°C, V
IN
= 12V, V
MSHDN,
V
SHDN1,3,5
= 0V (Notes 2, 5), unless otherwise noted.
MIN
1.2
3.17
4.85
TYP
1.25
3.30
5.05
320
550
15
25
360
4.5
130
0.8
C
T
= 390pF, I
LOAD
= 700mA, V
IN
= 10V
3
25
160
1.4
5
185
2.0
7
MAX
1.3
3.48
5.25
UNITS
V
V
V
µA
µA
µA
µA
µA
V
mV
mV
V
µs
LTC1267-ADJ, LTC1267-ADJ5: V
IN
= 9V
V
IN
= 9V
I
LOAD
= 700mA
I
LOAD
= 700mA
V
IN
= 12V, EXT V
CC
= 5V
V
IN
= 40V, EXT V
CC
= 5V
V
IN
= 12V, V
MSHDN
= 2V
V
IN
= 40V, V
MSHDN
= 2V
EXT V
CC
= 5V, Sleep Mode
V
IN
= 12V to 40V, EXT V
CC
= 0V, I
CC
= 20mA
Low Threshold (Forced)
High Threshold (Forced)
I
IN
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:
LTC1267/LTC1267-ADJ/LTC1267ADJ5: T
J
= T
A
+ (P
D
×
95°C/ W)
Note 2:
On LTC1267 versions which have MSHDN and SHDN1, 3, 5 pins,
they must be at ground potential for testing.
Note 3:
The LTC1267 V
IN
and EXT V
CC
current measurements exclude
MOSFET driver currents. When V
CC
power is derived from the output via
EXT V
CC
, the input current increases by (I
GATECHG
×
Duty Cycle)/Efficiency.
See Typical Performance Characteristics and Applications Information.
Note 4:
In applications where R
SENSE
is placed at ground potential, the
off-time increases approximately 40%.
Note 5:
The LTC1267/LTC1267-ADJ/LTC1267-ADJ5 are not tested and
quality-assurance sampled at – 40°C to 85°C. These specifications are
guaranteed by design and/or correlation.
Note 6:
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 EXT V
CC
powered from a 9V supply. See applications
information.
Note 7:
LTC1267-ADJ and LTC1267-ADJ5 are tested at an output of 3.3V
TYPICAL PERFORMANCE CHARACTERISTICS
5V Output Efficiency
vs Load Current
100
95
V
IN
= 10V
90
90
100
95
∆OUTPUT
VOLTAGE (mV)
EFFICIENCY (%)
85
V
IN
= 20V
80
75
70
65
60
0.01
0.1
1
LOAD CURRENT (A)
10
LTC1267 • G01
EFFICIENCY (%)
4
U W
3.3V Output Efficiency
vs Load Current
30
20
Load Regulation
V
IN
= 10V
10
0
–10
–20
–30
–40
–50
V
IN
= 10V
V
OUT
= 5V
V
IN
= 20V
V
OUT
= 3.3V
V
IN
= 10V
V
OUT
= 3.3V
85
V
IN
= 20V
80
75
70
65
60
0.01
0.1
1
LOAD CURRENT (A)
10
LTC1267 • G02
V
IN
= 20V
V
OUT
= 5V
–60
0
0.5
1.5
1.0
LOAD CURRENT
2.0
2.5
LTC1267 • G03
LTC1267
LTC1267-ADJ/LTC1267-ADJ5
TYPICAL PERFORMANCE CHARACTERISTICS
5V Output Efficiency
vs Line Voltage
100
95
90
LOGIC THRESHOLD
GATE, 1A
EFFICIENCY (%)
∆OUTPUT
VOLTAGE (mV)
EFFICIENCY (%)
85
80
75
70
65
60
0
5
10
LOGIC
THRESHOLD
GATE, 0.1A
STANDARD
THRESHOLD GATE, 1A
V
EXTVCC
= 9V
STANDARD
THRESHOLD GATE, 0.1A
V
EXTVCC
= 9V
35
40
15 20 25 30
INPUT VOLTAGE (V)
Operating Frequency
vs (V
IN
– V
OUT
)
2.0
NORMALIZED FREQUENCY (Hz)
V
OUT
= 5V
I
LOAD
= 700mA
1.5
SENSE VOLTAGE (mV)
OFF-TIME (µs)
1.0
0.5
0
0
5
15
20
10
(V
IN
– V
OUT
) VOLTAGE (V)
PI FU CTIO S
V
IN
:
Main Supply Input Pin.
EXT V
CC
:
External V
CC
Supply for the Regulators. See EXT
V
CC
Pin Connection.
V
CC
:
Output of the Internal 4.5V Linear Regulator, EXT V
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 EXT V
CC
voltage. Must be
closely decoupled to the power ground.
PGND:
Power Ground. Connect to the source of N-channel
MOSFET and the (–) terminal of C
IN
.
U W
NOTE 6
LTC1267 • G04
3.3V Output Efficiency
vs Line Voltage
100
95
90
NOTE 6
85
LOGIC
THRESHOLD
GATE, 0.1A
75
STANDARD
THRESHOLD GATE, 1A
70
V
EXTVCC
= 9V
80
65
60
0
5
10
LOGIC THRESHOLD
GATE, 1A
60
40
Line Regulation
NOTE 6
20
0
–20
–40
–60
STANDARD
THRESHOLD GATE, 0.1A
V
EXTVCC
= 9V
35
40
15 20 25 30
INPUT VOLTAGE (V)
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
LTC1267 • G05
LT1267 • G06
Off-Time vs Output Voltage
160
0°C
180
160
140
120
100
80
60
40
20
Current Sense Threshold Voltage
140
25°C
70°C
120
100
80
60
3.3V OUTPUT REGULATOR
40
20
25
MAXIMUM THRESHOLD
5V OUTPUT REGULATOR
MINIMUM THRESHOLD
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT VOLTAGE (V)
LTC1267 • F08
0
0
10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
LTC1267 • G09
LTC1267 • G07
U
U
U
(Applies to both regulator sections)
SGND:
Small-Signal Ground. Must be routed separately
from other grounds to the (–) terminal of C
OUT
.
PGATE:
Level Shifted Gate Drive for the Top P-channel
MOSFET. The voltage swing at the PGate pin is from V
IN
to
(V
IN
– V
CC
).
PDRIVE:
High Current Gate Drive for the Top P-channel
MOSFET. The PDrive pin swings from V
CC
to GND.
NGATE:
High Current Drive for the Bottom N-channel
MOSFET. The NGate pin swings from GND to V
CC
.
5
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