LTC1266
LTC1266-3.3/LTC1266-5
Synchronous Regulator
Controller for
N- or P-Channel MOSFETs
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
s
s
Ultrahigh 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
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.
APPLICATIO S
s
s
s
s
s
Notebook and Palmtop Computers
Portable Instruments
Cellular Telephones
DC Power Distribution Systems
GPS Systems
TYPICAL APPLICATIO
V
IN
4V TO 9V
D2
MBR0530T1
+
C
IN
100µF
×2
LOW BAT OUT
V
IN
LB
IN
PINV
PWR V
IN
LB
OUT
TDRIVE
SENSE
+
SENSE
–
BDRIVE
PGND
1000pF
N-CHANNEL
Si9410
D1
MBRS130LT3
1266 TA01
C
B
0.1µF
N-CHANNEL
Si9410
L*
5µH
100k
LOW BAT IN
LTC1266-3.3
0V = NORMAL
>1.5V = SHUTDOWN
R
C
470Ω
C
C
3300pF
SHDN
I
TH
C
T
BINH
SGND
V
OUT
3.3V
5A
EFFICIENCY (%)
R
SENSE
0.02Ω
+
C
T
180pF
C
OUT
330µF
×
2
*TOKO 919AS-4R7M
Figure 1. High Efficiency Step-Down Converter
U
LTC1266-3.3 Efficiency
100
V
IN
= 5V
95
90
85
80
0.01
0.1
1
LOAD CURRENT (A)
5
1266 TA02
U
U
1
LTC1266
LTC1266-3.3/LTC1266-5
ABSOLUTE
(Note 1)
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
SHDN Voltage (Pin 11) ............................. 12V to – 0.3V
PINV, BINH, LB
IN
(Pins 3, 4, 13)................20V to – 0.3V
LB
OUT
Output Current ........................................... 12mA
Operating Ambient Temperature Range ...... 0°C to 70°C
Industrial Temperature Range ................ – 40°C to 85°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
LTC1266CS
LTC1266CS-3.3
LTC1266CS-5
LTC1266ACS
LTC1266IS
LTC1266IS-3.3
LTC1266IS-5
LTC1266AIS
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.
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 10V, V
SHDN
= V
BINH
= 0V unless otherwise noted.
SYMBOL
V
FB
PARAMETER
Feedback Voltage
LTC1266ACS
LTC1266CS
I
FB
V
OUT
Feedback Current (LTC1266 Only)
Regulated Output Voltage
LTC1266CS-3.3
LTC1266CS-5
Output Ripple (Burst Mode Operation) I
LOAD
= 150mA
∆V
OUT
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
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
q
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
V
IN
= 9V, I
LOAD
= 700mA, V
PINV
= V
PWR
= 14V,
Topside Switch = N-Ch
q
q
q
MIN
TYP
MAX
UNITS
1.252
1.210
1.265
1.265
0.2
1.278
1.290
1
V
IN
= 9V, I
LOAD
= 700mA, V
PINV
= V
PWR
= 14V,
Topside Switch = N-Ch
q
q
3.23
4.90
3.33
5.05
50
3.43
5.20
mV
P-P
40
40
65
25
100
40
3.0
250
50
40
5
5
mV
mV
mV
mV
mV
mV
mA
µA
µA
µA
µA
µA
– 40
– 40
0
0
40
15
60
25
2.1
170
25
20
1
1
Output Voltage Load Regulation
LTC1266-3.3
LTC1266-3.3
LTC1266-5
LTC1266-5
I
Q1
V
IN
Pin DC Supply Current (Note 3)
Normal Mode
Sleep Mode
Shutdown
PWR V
IN
DC Supply Current (Note 3)
Normal Mode
Sleep Mode
Shutdown
I
Q2
2
U
V
V
µA
V
V
W
U
U
W W
W
LTC1266
LTC1266-3.3/LTC1266-5
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 10V, V
SHDN
= V
BINH
= 0V unless otherwise noted.
SYMBOL
V
SENSE 1
PARAMETER
Current Sense Threshold
(Burst Mode Operation Enabled)
LTC1266
LTC1266-3.3
LTC1266-5
V
SENSE 2
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 4)
Max On-Time
Driver Output Transition Times (Note 7)
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
0V < V
SHDN
< 8V, V
IN
= 16V
0V < V
PINV
< 18V, V
IN
= 18V
V
IN
= 7V
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
1.30
3.43
5.20
1.14
1.17
1.25
1.30
25
8
0.2
1
1.35
1.42
200
V
V
V
V
V
nA
mA
µA
50
4
0.8
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
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)
V
SENSE –
= V
OUT
+ 100mV (Forced)
V
SENSE –
= V
OUT
– 100mV (Forced)
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
TYP
MAX
UNITS
135
135
135
25
155
25
155
25
155
175
175
175
mV
mV
mV
mV
mV
mV
135
135
135
0.6
– 20
155
– 20
155
– 20
155
0.8
1.2
0.2
1.2
0.2
70
2
5
60
100
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
V
LBTRIP
I
LBLEAK
I
LBSINK
I
LBIN
– 40°C < T
A
< 85°C (Note 5), V
IN
= 10V, unless otherwise noted.
SYMBOL
V
FB
PARAMETER
Feedback Voltage
LTC1266AIS
LTC1266CS, LTC1266IS
V
OUT
Regulated Output Voltage
LTC1266CS-3.3, LTC1266IS-3.3
LTC1266CS-5, LTC1266IS-5
V
IN
= 9V, I
LOAD
= 700mA, V
PINV
= V
PWR
= 14,
Topside Switch = N-Ch
3.23
4.90
3.33
5.05
3.43
5.20
V
V
CONDITIONS
V
IN
= 9V, I
LOAD
= 700mA, V
PINV
= V
PWR
= 14V,
Topside Switch = N-Ch
1.246
1.210
1.265
1.265
1.290
1.290
V
V
MIN
TYP
MAX
UNITS
3
LTC1266
LTC1266-3.3/LTC1266-5
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q1
PARAMETER
V
IN
Pin DC Supply Current (Note 3)
Normal Mode
Sleep Mode
Shutdown
PWR V
IN
DC Supply Current (Note 3)
Normal Mode
Sleep Mode
Shutdown
Current Sense Threshold
(Burst Mode Operation Enabled)
LTC1266CS, LTC1266IS
LTC1266CS
LTC1266IS
LTC1266-3.3, LTC1266-5 (I and C)
LTC1266CS-3.3, LTC1266CS-5
LTC1266IS-3.3, LTC1266IS-5
Current Sense Threshold
(Burst Mode Operation Disabled)
LTC1266CS, LTC1266IS
LTC1266CS
LTC1266IS
LTC1266-3.3, LTC1266-5 (I and C)
LTC1266CS-3.3, LTC1266CS-5
LTC1266IS-3.3, LTC1266IS-5
Shutdown Pin Threshold
Off-Time (Note 4)
CONDITIONS
– 40°C < T
A
< 85°C (Note 5), V
IN
= 10V, unless otherwise noted.
MIN
TYP
2.1
170
25
20
1
1
MAX
3.3
260
60
50
7
7
UNITS
mA
µA
µA
µA
µA
µA
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
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–
= 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
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–
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)
C Grade
I Grade
C
T
= 390pF, I
LOAD
= 700mA, C Grade
C
T
= 390pF, I
LOAD
= 700mA, I Grade
130
130
130
130
0.55
0.50
3.8
3.8
135
135
135
135
I
Q2
V
SENSE1
25
155
155
25
155
155
180
190
180
190
mV
mV
mV
mV
mV
mV
V
SENSE2
–20
155
155
–20
155
155
0.8
0.8
5
5
185
195
185
195
2
2
6.5
7.0
mV
mV
mV
mV
mV
mV
V
V
µs
µs
V
SHDN
t
OFF
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
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 3:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 4:
In applications where R
SENSE
is placed at ground potential, the off-
time increases approximately 40%.
Note 5:
The LTC1266CS, LTC1266CS-3.3, LTC1266-5 and LTC1266ACS
are not tested and not quality assurance sampled at – 40°C and 85°C.
These specifications are guaranteed by design and/or correlation. The
LTC1266IS, LTC1266IS-3.3, LTC1266IS-5 and LTC1266AIS are
guaranteed and tested over the – 40°C to 85°C operating temperature
range.
Note 6:
Unless otherwise noted the specifications for the LTC1266A are
the same as those for the LTC1266.
Note 7:
t
r
and t
f
are measured at 10% and 90% levels.
4
LTC1266
LTC1266-3.3/LTC1266-5
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Input Voltage
100
95
I
LOAD
= 2.5A
EFFICIENCY (%)
90
I
LOAD
= 5A
85
80
75
–30
FIGURE 1 CIRCUIT
∆V
OUT
(mV)
∆V
OUT
(mV)
I
LOAD
= 100mA
70
3
4
5
6
7
INPUT VOLTAGE (V)
Efficiency vs Input Voltage
100
95
EFFICIENCY (%)
FIGURE 11 CIRCUIT
I
LOAD
= 1A
I
LOAD
= 2.5A
∆V
OUT
(mV)
∆V
OUT
(mV)
90
85
80
75
70
I
LOAD
= 100mA
0
4
12
8
INPUT VOLTAGE (V)
V
IN
DC Supply Current
3.0
2.5
25
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
0
4
12
8
INPUT VOLTAGE (V)
16
20
1266 G07
U W
8
1266 G01
Line Regulation
40
30
20
10
0
–10
–20
Load Regulation
20
FIGURE 1 CIRCUIT
V
IN
= 9V (Burst Mode
OPERATION ENABLED)
V
IN
= 5V
10
0
–10
–20
–30
–40
–50
V
IN
= 5V (Burst Mode
OPERATION INHIBITED)
FIGURE 1 CIRCUIT
I
LOAD
= 1A
9
– 40
3
4
5
6
7
INPUT VOLTAGE (V)
8
9
1266 G02
0
1
3
2
LOAD CURRENT (A)
4
5
1266 G03
Line Regulation
40
30
20
10
0
–10
–20
–30
– 40
Load Regulation
30
FIGURE 11 CIRCUIT
FIGURE 11 CIRCUIT
I
LOAD
= 1A
20
10
0
–10
V
IN
= 5V
–20
–30
–40
V
IN
= 5V (Burst Mode
OPERATION INHIBITED)
V
IN
= 12V (Burst Mode
OPERATION ENABLED)
16
20
1266 G04
0
4
8
12
16
1266 G05
0
0.5
INPUT VOLTAGE (V)
2.0
1.5
1.0
LOAD CURRENT (A)
2.5
3.0
1266 G06
Power V
IN
DC Supply Current
50
Supply Current in Shutdown
20
ACTIVE MODE
40
V
IN
15
30
10
20
5
10
PWR V
IN
16
20
1266 G08
0
4
12
8
INPUT VOLTAGE (V)
0
0
5
15
10
INPUT VOLTAGE (V)
20
1266 G09
5
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