LT1610
1.7MHz, Single Cell
Micropower
DC/DC Converter
FEATURES
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Uses Tiny Capacitors and Inductor
Internally Compensated
Low Quiescent Current: 30
µ
A
Operates with V
IN
as Low as 1V
3V at 30mA from a Single Cell
5V at 200mA from 3.3V
High Output Voltage Capability: Up to 28V
Low Shutdown Current: < 1µA
Automatic Burst Mode
TM
Switching at Light Load
Low V
CESAT
Switch: 300mV at 300mA
8-Lead MSOP and SO Packages
The LT
®
1610 is a micropower fixed frequency DC/DC
converter that operates from an input voltage as low as 1V.
Intended for small, low power applications, it switches at
1.7MHz, allowing the use of tiny capacitors and inductors.
The device can generate 3V at 30mA from a single cell
(1V) supply. An internal compensation network can be
connected to the LT1610’s V
C
pin, eliminating two exter-
nal components. No-load quiescent current of the LT1610
is 30µA, and the internal NPN power switch handles a
300mA current with a voltage drop of 300mV.
The LT1610 is available in 8-lead MSOP and SO packages.
APPLICATIO S
s
s
s
s
s
Pagers
Cordless Phones
Battery Backup
LCD Bias
Portable Electronic Equipment
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
L1
4.7µH
D1
V
OUT
3V
30mA
R1
1M
85
V
OUT
= 3V
80
V
IN
= 1.25V
75
V
IN
= 1.5V
6
V
IN
3
5
SW
FB
LT1610
2
+
1 CELL
C1
22µF
8
R2
681k
GND
7
+
C2
22µF
EFFICIENCY (%)
SHDN
70
65
60
55
COMP
V
C
1
PGND
4
C1, C2: AVX TAJA226M006R
D1: MOTOROLA MBR0520
L1: MURATA LQH1C4R7
1610 F01
50
0.1
1
10
LOAD CURRENT (mA)
100
1610 TA01
Figure 1. 1-Cell to 3V Step-Up Converter
U
Efficiency
V
IN
= 1V
U
U
1
LT1610
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
V
IN
Voltage ................................................................ 8V
SW Voltage ............................................... – 0.4V to 30V
FB Voltage ..................................................... V
IN
+ 0.3V
V
C
Voltage ................................................................ 2V
COMP Voltage .......................................................... 2V
Current into FB Pin ..............................................
±1mA
SHDN Voltage ............................................................ 8V
PACKAGE/ORDER INFORMATION
TOP VIEW
V
C
FB
SHDN
PGND
1
2
3
4
8
7
6
5
COMP
GND
V
IN
SW
ORDER PART
NUMBER
LT1610CMS8
MS8 PART MARKING
LTDT
V
C
1
FB 2
SHDN 3
PGND 4
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
Consult factory for Military grade parts.
The
q
denotes specifications which apply over the specified temperature
range, otherwise specifications are at T
A
= 25°C. Commercial grade 0°C to 70°C, V
IN
= 1.5V, V
SHDN
= V
IN
, unless otherwise noted.
(Note 2)
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage
Quiescent Current
Quiescent Current in Shutdown
FB Pin Bias Current
Reference Line Regulation
1V
≤
V
IN
≤
2V (25°C, 0°C)
1V
≤
V
IN
≤
2V (70°C)
2V
≤
V
IN
≤
8V (25°C, 0°C)
2V
≤
V
IN
≤
8V (70°C)
∆I
= 2µA
q
q
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
V
SHDN
= 1.5V, Not Switching
V
SHDN
= 0V, V
IN
= 2V
V
SHDN
= 0V, V
IN
= 5V
q
Error Amp Transconductance
Error Amp Voltage Gain
Switching Frequency
Maximum Duty Cycle
2
U
U
W
W W
U
W
Maximum Junction Temperature ......................... 125°C
Operating Temperature Range (Note 1)
Commercial ............................................. 0°C to 70°C
Extended Commercial (Note 2) .......... – 40°C to 85°C
Industrial ........................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
8
7
6
5
COMP
GND
V
IN
SW
ORDER PART
NUMBER
LT1610CS8
LT1610IS8
S8 PART MARKING
1610
1610I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 120°C/W
MIN
TYP
0.9
MAX
1
8
1.26
60
0.5
1.0
80
1
2
0.15
0.2
UNITS
V
V
V
µA
µA
µA
nA
%/V
%/V
%/V
%/V
µmhos
V/V
1.20
1.23
30
0.01
0.01
27
0.6
0.03
25
100
1.4
77
75
1.7
80
2
95
95
MHz
%
%
LT1610
The
q
denotes specifications which apply over the specified temperature
range, otherwise specifications are at T
A
= 25°C. Commercial grade 0°C to 70°C, V
IN
= 1.5V, V
SHDN
= V
IN
, unless otherwise noted.
(Note 2)
PARAMETER
Switch Current Limit
Switch V
CESAT
Switch Leakage Current
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Bias Current
V
SHDN
= 3V
V
SHDN
= 0V
10
0.01
CONDITIONS
(Note 3)
I
SW
= 300mA
q
ELECTRICAL CHARACTERISTICS
MIN
450
TYP
600
300
0.01
MAX
900
350
400
1
0.3
0.1
UNITS
mA
mV
mV
µA
V
V
µA
µA
V
SW
= 5V
1
The
q
denotes specifications which apply over the specified temperature range, otherwise specifications are at T
A
= 25°C.
Industrial grade – 40°C to 85°C, V
IN
= 1.5V, V
SHDN
= V
IN
, unless otherwise noted.
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage
Quiescent Current
Quiescent Current in Shutdown
FB Pin Bias Current
Reference Line Regulation
Error Amp Transconductance
Error Amp Voltage Gain
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
Switch V
CESAT
Switch Leakage Current
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Bias Current
V
SHDN
= 3V
V
SHDN
= 0V
10
0.01
I
SW
= 300mA
q
q
CONDITIONS
T
A
= 85°C
T
A
= – 40°C
MIN
TYP
0.9
MAX
1
1.25
8
1.26
60
0.5
1.0
80
0.15
0.2
UNITS
V
V
V
V
µA
µA
µA
nA
%/V
%/V
µmhos
V/V
1.20
1.23
30
0.01
0.01
V
SHDN
= 0V, V
IN
= 2V
V
SHDN
= 0V, V
IN
= 5V
q
27
0.03
25
100
2V
≤
V
IN
≤
8V (– 40°C)
2V
≤
V
IN
≤
8V (85°C)
∆I
= 2µA
(Note 4)
(Note 4)
q
q
1.4
77
75
450
1.7
80
600
300
0.01
2
95
95
900
350
400
1
0.3
0.1
MHz
%
%
mA
mV
mV
µA
V
V
µA
µA
V
SW
= 5V
1
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LT1610C is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at – 40°C and 85°C. The
LT1610I is guaranteed to meet the extended temperature limits.
Note 3:
Current limit guaranteed by design and/or correlation to static test.
Current limit is affected by duty cycle due to ramp generator. See Block
Diagram.
Note 4:
Not 100% tested at 85°C.
3
LT1610
TYPICAL PERFOR A CE CHARACTERISTICS
V
CESAT
vs Current
600
800
700
600
500
400
300
200
–50
CURRENT LIMIT (mA)
500
T
A
= 85°C
V
CESAT
(mV)
400
T
A
= 25°C
300
T
A
= – 40°C
200
SWITCH CURRENT LIMIT (mA)
100
0
100
500
200
300
400
SWITCH CURRENT (mA)
Oscillator Frequency
vs Input Voltage
2.50
2.25
SWITCHING FREQUENCY (MHz)
T
A
= 25°C
QUIESCENT CURRENT (µA)
2.00
FEEDBACK VOLTAGE (V)
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
0
1
2
6
4
3
5
INPUT VOLTAGE (V)
7
8
SHDN Pin Current
vs SHDN Pin Voltage
50
V
OUT
50mV/DIV
AC COUPLED
I
L1
100mA/DIV
I
LOAD
31mA
1mA
40
SHDN CURRENT (µA)
30
20
10
0
0
1
2
4
3
5
6
SHDN VOLTAGE (V)
7
8
4
U W
Current Limit (DC = 30%)
vs Temperature
800
700
600
500
400
300
200
100
0
–25
0
25
50
TEMPERATURE (°C)
75
100
1610 G02
Current Limit vs Duty Cycle
T
A
= 25°C
600
0
10 20 30 40 50 60 70
DUTY CYCLE (%)
80 90 100
1610 G03
1610 G01
Feedback Voltage
1.240
1.235
1.230
1.225
1.220
1.215
1.210
–50
40
35
30
25
20
15
10
5
Quiescent Current
vs Temperature
–25
0
25
50
TEMPERATURE (°C)
75
100
1610 G05
0
– 50
– 25
0
50
25
TEMPERATURE (°C)
75
100
1610 G06
1610 G04
Transient Response,
Circuit of Figure 1
V
OUT
20mV/DIV
AC COUPLED
SWITCH
VOLTAGE
2V/DIV
SWITCH
CURRENT
50mA/DIV
V
IN
= 1.25V
V
OUT
= 3V
500µs/DIV
1610 TA08
Burst Mode Operation,
Circuit of Figure 1
V
IN
= 1.25V
V
OUT
= 3V
I
LOAD
= 3mA
20µs/DIV
1610 TA08
1610 G07
LT1610
PIN FUNCTIONS
V
C
(Pin 1):
Error Amplifier Output. Frequency compensa-
tion network must be connected to this pin, either internal
(COMP pin) or external series RC to ground. 220kΩ/
220pF typical value.
FB (Pin 2):
Feedback Pin. Reference voltage is 1.23V.
Connect resistive divider tap here. Minimize trace area at
FB. Set V
OUT
according to V
OUT
= 1.23V (1 + R1/R2).
SHDN (Pin 3):
Shutdown. Ground this pin to turn off
device. Tie to 1V or more to enable.
PGND (Pin 4):
Power Ground. Tie directly to local ground
plane.
SW (Pin 5):
Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to keep EMI down.
V
IN
(Pin 6):
Input Supply Pin. Must be locally bypassed.
GND (Pin 7):
Signal Ground. Carries all device ground
current except switch current. Tie to local ground plane.
COMP (Pin 8):
Internal Compensation Network. Tie to V
C
pin, or let float if external compensation is used. Output
capacitor must be tantalum if COMP pin is used for com-
pensation.
BLOCK DIAGRA
V
IN
6
V
OUT
R1
(EXTERNAL)
FB
FB
2
Q1
R2
(EXTERNAL)
RAMP
GENERATOR
1.7MHz
OSCILLATOR
Figure 2. LT1610 Block Diagram
+
Σ
–
W
U
U
U
V
IN
R5
40k
R6
40k
+
A1
g
m
1 V
C
8
COMP
R
C
C
C
SHUTDOWN
3 SHDN
7 GND
–
Q2
×
10
R3
30k
R4
140k
+
ENABLE
BIAS
–
5 SW
COMPARATOR
FF
A2
R
S
Q
DRIVER
Q3
+
A=3
0.15Ω
–
4
PGND
1610 F02
5
