LTC1266
LTC1266-3.3/LTC1266-5
Synchronous Regulator
Controller for
N- or P-Channel MOSFETs
DESCRIPTIO
The LTC
®
1266 series is a family of synchronous switching
regulator controllers featuring automatic Burst Mode
TM
operation to maintain high efficiencies at low output
currents. These devices drive external power MOSFETs at
switching frequencies up to 400kHz using a constant off-
time current mode architecture providing constant ripple
current in the inductor. They can drive either an N-channel
or a P-channel topside MOSFET.
The operating current level 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 regu-
lation limited only by the R
DS(ON)
of the topside MOSFET
(when using the P-channel) and the resistance of the
inductor and current sense resistor.
The LTC1266 series combines synchronous switching for
maximum efficiency at high currents with an automatic
low current operating mode, called Burst Mode operation,
which reduces switching losses. Standby power is re-
duced to only 1mW at V
IN
= 5V (at I
OUT
= 0). Load currents
in Burst Mode operation are typically 0mA to 500mA.
, 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
s
s
s
s
s
Ultra-High Efficiency: Over 95% Possible
Drives N-Channel MOSFET for High Current or
P-Channel MOSFET for Low Dropout
Pin Selectable Burst Mode Operation
1% Output Accuracy (LTC1266A)
Pin Selectable Phase of Topside Driver for Boost
or Step-Down Operation
Wide V
IN
Range: 3.5V to 20V
On-Chip Low-Battery Detector
High Efficiency Maintained over Large Current Range
Low 170µA Standby Current at Light Loads
Current Mode Operation for Excellent Line and Load
Transient Response
Logic Controlled Micropower Shutdown: I
Q
< 40µA
Short Circuit Protection
Synchronous Switching with Nonoverlaping Gate Drives
Available in 16-Pin Narrow SO Package
APPLICATI
s
s
s
s
s
S
Notebook and Palmtop Computers
Portable Instruments
Cellular Telephones
DC Power Distribution Systems
GPS Systems
TYPICAL APPLICATI
V
IN
4V TO 9V
D2
MBR0530T1
+
C
IN
100µF
×2
V
IN
PWR V
IN
LB
OUT
TDRIVE
SENSE
+
SENSE
–
BDRIVE
PGND
1000pF
N-CHANNEL
Si9410
N-CHANNEL
Si9410
LOW BAT OUT
C
B
0.1µF
L*
5µH
LOW BAT IN
LB
IN
PINV
LTC1266-3.3
0V = NORMAL
>1.5V = SHUTDOWN
R
C
470Ω
C
C
3300pF
SHDN
I
TH
C
T
BINH
SGND
R
SENSE
0.02Ω
EFFICIENCY (%)
100k
V
OUT
3.3V
5A
C
OUT
330µF
×
2
+
D1
MBRS130LT3
LTC1266 • TA01
C
T
180pF
*COILTRONICS CTXO212801
Figure 1. High Efficiency Step-Down Converter
U
UO
UO
LTC1266-3.3 Efficiency
100
V
IN
= 5V
95
90
85
80
0.01
0.1
1
LOAD CURRENT (A)
5
LTC1266 • TA02
1
LTC1266
LTC1266-3.3/LTC1266-5
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
TDRIVE 1
PWR V
IN
2
PINV 3
BINH 4
V
IN
5
C
T
6
I
TH
7
SENSE
–
8
16 BDRIVE
15 PGND
14 LB
OUT
13 LB
IN
12 SGND
11 SHDN
10 V
FB
(NC*)
9 SENSE
+
Input Supply Voltage (Pins 2, 5) ............... 20V to – 0.3V
Continuous Output Current (Pins 1, 16) .............. 50mA
Sense Voltages (Pins 8, 9)........................ 13V to – 0.3V
PINV, BINH, SHDN, LB
IN
(Pins 3, 4, 11, 13) ................................. 20V to – 0.3V
LB
OUT
Output Current ........................................... 12mA
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
ORDER PART
NUMBER
LTC1266CS
LTC1266CS-3.3
LTC1266CS-5
LTC1266ACS
S PACKAGE
16-LEAD PLASTIC SO
*FIXED OUTPUT VERSIONS
T
JMAX
= 125°C,
θ
JA
= 110°C/ W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
FB
PARAMETER
Feedback Voltage
LTC1266ACS
LTC1266CS
Feedback Current (LTC1266 Only)
Regulated Output Voltage
LTC1266CS-3.3
LTC1266CS-5
CONDITIONS
T
A
= 25°C, V
IN
= 10V, V
SHDN
= V
BINH
= 0V unless otherwise noted.
MIN
q
q
q
TYP
1.275
1.25
0.2
MAX
UNITS
V
V
µA
V
V
mV
P-P
V
IN
= 9V, I
LOAD
= 700mA, V
PINV
= V
PWR
,
Topside Switch = N-Ch
1.210
1.290
1
3.43
5.20
I
FB
V
OUT
V
IN
= 9V, I
LOAD
= 700mA, V
PINV
= V
PWR
,
Topside Switch = N-Ch, V
PWR
= 14V
q
q
3.23
4.90
3.33
5.05
50
∆V
OUT
Output Ripple (Burst Mode Operation) I
LOAD
= 150mA
Output Voltage Line Regulation
I
LOAD
= 50mA
V
PINV
= 0V, Topside Switch = P-Ch, V
IN
= 7V to 12V
V
PINV
= V
PWR
, Topside Switch = N-Ch, V
IN
= 7V to 12V
Output Voltage Load Regulation
LTC1266-3.3
LTC1266-3.3
LTC1266-5
LTC1266-5
5mA < I
LOAD
< 2A, R
SENSE
= 0.05Ω
Burst Mode Operation Enabled, V
BINH
= 0V
Burst Mode Operation Inhibited, V
BINH
= 2V
Burst Mode Operation Enabled, V
BINH
= 0V
Burst Mode Operation Inhibited, V
BINH
= 2V
3.5V < V
IN
< 18V
3.5V < V
IN
< 18V
V
SHDN
= 2.1V, 3.5V < V
IN
< 18V
3.5V < PWR V
IN
< 18V
3.5V < PWR V
IN
< 18V
V
SHDN
= 2.1V, 3.5V < PWR V
IN
< 18V
V
BINH
= 0V
V
SENSE –
= 3.3V, V
FB
= V
OUT
/2.64 + 25mV (Forced)
V
SENSE –
= 3.3V, V
FB
= V
OUT
/2.64 – 25mV (Forced)
V
SENSE –
= V
OUT
+ 100mV (Forced)
V
SENSE –
= V
OUT
– 100mV (Forced)
V
SENSE –
= V
OUT
+ 100mV (Forced)
V
SENSE –
= V
OUT
– 100mV (Forced)
q
q
q
q
q
q
q
–40
–40
0
0
40
15
60
25
2.1
170
25
20
1
1
40
40
65
25
100
40
3.0
250
50
40
5
5
I
Q1
V
IN
Pin DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
PWR V
IN
DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
Current Sense Threshold
(Burst Mode Operation Enabled)
LTC1266
LTC1266-3.3
LTC1266-5
I
Q2
V
SENSE 1
135
135
135
25
155
25
155
25
155
175
175
175
2
U
mV
mV
mV
mV
mV
mV
mA
µA
µA
µA
µA
µA
mV
mV
mV
mV
mV
mV
W
U
U
W W
W
LTC1266
LTC1266-3.3/LTC1266-5
ELECTRICAL CHARACTERISTICS
SYMBOL
V
SENSE 2
PARAMETER
Current Sense Threshold
(Burst Mode Operation Disabled)
LTC1266
LTC1266-3.3
LTC1266-5
V
SHDN
I
SHDN
I
PINV
V
BINH
I
BINH
I
CT
t
OFF
t
MAX
t
r
, t
f
V
CLAMP
Shutdown Pin Threshold
Shutdown Pin Input Current
Phase Invert Pin Input Current
Burst Mode Operation
Inhibit Pin Threshold
Burst Mode Operation
Inhibit Pin Input Current
C
T
Pin Discharge Current
Off-Time (Note 3)
Max On-Time
Driver Output Transition Times
Output Voltage Clamp in
Burst Mode Operation Inhibit
LTC1266
LTC1266-3.3
LTC1266-5
Low-Battery Trip Point
Max Leakage Current into Pin 14
Max Sink Current into Pin 14
Max Leakage Current into Pin 13
CONDITIONS
V
BINH
= 2.1V
T
A
= 25°C, V
IN
= 10V, V
SHDN
= V
BINH
= 0V unless otherwise noted.
MIN
TYP
MAX
UNITS
V
SENSE –
= 3.3V, V
FB
= V
OUT
/2.64 + 25mV (Forced)
V
SENSE –
= 3.3V, V
FB
= V
OUT
/2.64 – 25mV (Forced)
V
SENSE –
= V
OUT
+ 100mV (Forced)
V
SENSE –
= V
OUT
– 100mV (Forced)
V
SENSE –
= V
OUT
+ 100mV (Forced)
V
SENSE –
= V
OUT
– 100mV (Forced)
0V < V
SHDN
< 8V, V
IN
= 16V
0V < V
PINV
< 18V, V
IN
= 18V
q
q
q
135
135
135
0.6
– 20
155
– 20
155
– 20
155
0.8
1.2
0.2
175
175
175
2
5
1
2
1
90
10
6
200
mV
mV
mV
mV
mV
mV
V
µA
µA
V
µA
µA
µA
µs
µs
ns
0.8
0V < V
BINH
< 18V, V
IN
= 18V
V
SENSE +
= V
OUT
– 100mV, V
SENSE –
= V
OUT
– 300mV
V
OUT
= 0V
C
T
= 390pF, I
LOAD
= 700mA
V
OUT
= 0V, V
IN
= 18V
C
L
= 3000pF (Pins 1, 16), V
IN
= 6V
V
BINH
= 2.1V
Measured at V
FB
Measured at V
SENSE –
Measured at V
SENSE –
V
IN
= 5V
V
IN
= 12V
V
LBOUT
= 18V, V
LBIN
= 2V
V
LBOUT
= 1V, V
LBIN
= 0V, 2.5V < V
IN
< 18V
V
LBIN
= 18V
1
1.14
1.17
50
4
1.2
0.2
70
2
5
60
100
1.30
3.43
5.20
1.25
1.30
25
8
0.2
1
1.35
1.42
200
V
V
V
V
V
nA
mA
µA
V
LBTRIP
I
LBLEAK
I
LBSINK
I
LBIN
– 40°C < T
A
< 85°C (Note 4), V
IN
= 10V, unless otherwise noted.
SYMBOL
V
FB
V
OUT
PARAMETER
Feedback Voltage (LTC1266 only)
Regulated Output Voltage
LTC1266-3.3
LTC1266-5
V
IN
Pin DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
PWR V
IN
DC Supply Current (Note 2)
Normal Mode
Sleep Mode
Shutdown
CONDITIONS
V
IN
= 9V, I
LOAD
= 700mA
V
IN
= 9V, I
LOAD
= 700mA
3.23
4.90
3.5V < V
IN
< 18V
3.5V < V
IN
< 18V
V
SHUTDOWN
= 2.1V, 3.5V < V
IN
< 18V
3.5V < PWR V
IN
< 18V
3.5V < PWR V
IN
< 18V
V
SHUTDOWN
= 2.1V, 3.5V < PWR V
IN
< 18V
3.33
5.05
2.1
170
25
20
1
1
3.43
5.20
3.3
260
60
50
7
7
V
V
mA
µA
µA
µA
µA
µA
MIN
1.21
TYP
1.25
MAX
1.29
UNITS
V
I
Q1
I
Q2
3
LTC1266
LTC1266-3.3/LTC1266-5
ELECTRICAL CHARACTERISTICS
SYMBOL
V
SENSE1
PARAMETER
Current Sense Threshold
(Burst Mode Operation Enabled)
LTC1266
LTC1266-3.3, LTC1266-5
Sense 2
Current Sense Threshold
(Burst Mode Operation Disabled)
LTC1266
LTC1266-3.3, LTC1266-5
V
SHDN
t
OFF
Shutdown Pin Threshold
Off-Time (Note 3)
C
T
= 390pF, I
LOAD
= 700mA
CONDITIONS
V
BINH
= 0V
V
SENSE–
= 3.3V, V
FB
= V
OUT
/2.64 + 25mV (Forced)
V
SENSE–
= 3.3V, V
FB
= V
OUT
/2.64 – 25mV (Forced)
V
SENSE–
= V
OUT
+ 100mV (Forced)
V
SENSE–
= V
OUT
– 100mV (Forced)
V
BINH
= 2.1V
V
SENSE–
3.3V, V
FB
= V
OUT
/2.64 + 25mV (Forced)
V
SENSE–
3.3V, V
FB
= V
OUT
/2.64 – 25mV (Forced)
V
SENSE–
= V
OUT
+ 100mV (Forced)
V
SENSE–
= V
OUT
– 100mV (Forced)
130
130
0.55
3.8
–20
155
–20
155
0.8
5
185
185
2
6.5
mV
mV
mV
mV
V
µs
135
135
25
155
25
155
180
180
mV
mV
mV
mV
MIN
TYP
MAX
UNITS
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:
T
J
= T
A
+ (P
D
×
110°C/W)
Note 2:
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 LTC1266, LTC1266-3.3, and LTC1266-5 are not tested and
not quality assurance sampled at – 40°C and 85°C. These specifications
are guaranteed by design and/or correlation.
Note 5:
Unless otherwise noted the specifications for the LTC1266A are
the same as those for the LTC1266.
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Input Voltage
100
95
I
LOAD
= 2.5A
EFFICIENCY (%)
FIGURE 1 CIRCUIT
90
∆V
OUT
(mV)
I
LOAD
= 5A
85
80
75
70
I
LOAD
= 100mA
∆V
OUT
(mV)
3
4
5
6
7
INPUT VOLTAGE (V)
4
U W
8
9
LTC1266 • TPC01
Line Regulation
40
30
20
10
0
–10
–20
–30
– 40
3
4
5
6
7
INPUT VOLTAGE (V)
8
9
20
Load Regulation
FIGURE 1 CIRCUIT
V
IN
= 9V (Burst Mode
OPERATION ENABLED)
V
IN
= 5V
FIGURE 1 CIRCUIT
I
LOAD
= 1A
10
0
–10
–20
–30
–40
–50
0
1
3
2
LOAD CURRENT (A)
4
5
V
IN
= 5V (Burst Mode
OPERATION INHIBITED)
LTC1266 • TPC02
LTC1266 • TPC03
LTC1266
LTC1266-3.3/LTC1266-5
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Input Voltage
100
95
EFFICIENCY (%)
FIGURE 11 CIRCUIT
I
LOAD
= 1A
I
LOAD
= 2.5A
90
∆V
OUT
(mV)
∆V
OUT
(mV)
85
80
75
70
I
LOAD
= 100mA
0
4
12
8
INPUT VOLTAGE (V)
V
IN
DC Supply Current
3.0
2.5
SUPPLY CURRENT (mA)
SUPPLY CURRENT (µA)
2.0
1.5
1.0
0.5
0
ACTIVE MODE
SUPPLY CURRENT (µA)
SLEEP MODE
SLEEP MODE
0
4
12
8
INPUT VOLTAGE (V)
16
20
0
0
4
12
8
INPUT VOLTAGE (V)
16
20
0
0
5
PWR V
IN
15
10
INPUT VOLTAGE (V)
20
LTC1266 • TPC09
Off-Time vs Output Voltage
100
V
SENSE
–
= V
OUT
NORMALIZED FREQUENCY
80
OFF-TIME (µs)
2.0
1.5
1.0
0.5
0
25°C
70°C
60
SENSE VOLTAGE (mV)
40
20
LTC1266-3.3
0
0
1
LTC1266-5
3
4
2
OUTPUT VOLTAGE (V)
U W
16
LTC1266 • TPC04
LTC1266 • TPC07
LTC1266 • TPC10
Line Regulation
40
30
20
10
0
–10
–20
–30
– 40
Load Regulation
30
FIGURE 11 CIRCUIT
20
10
0
–10
V
IN
= 5V
–20
–30
–40
V
IN
= 5V (Burst Mode
OPERATION INHIBITED)
V
IN
= 12V (Burst Mode
OPERATION ENABLED)
FIGURE 11 CIRCUIT
I
LOAD
= 1A
20
0
4
8
12
16
LTC1266 • TPC05
0
0.5
INPUT VOLTAGE (V)
2.0
1.5
1.0
LOAD CURRENT (A)
2.5
3.0
LTC1266 • TPC06
Power V
IN
DC Supply Current
25
50
Supply Current in Shutdown
20
ACTIVE MODE
40
V
IN
15
30
10
20
5
10
Operating Frequency
vs (V
IN
– V
OUT
) Voltage
3.0
2.5
V
OUT
= 3.3V
0°C
LTC1266 • TPC08
Current Sense Threshold Voltage
200
MAX THRESHOLD
150
100
MIN THRESHOLD (Burst Mode
OPERATION ENABLED)
MIN THRESHOLD (Burst Mode
OPERATION INHIBIT)
50
0
5
0
2
6
8
10 12
4
(V
IN
– V
OUT
) VOLTAGE (V)
14
16
–50
0
20
60
40
TEMPERATURE (°C)
80
100
LTC1266 • TPC11
LTC1266 • TPC12
5
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