Linear Technology LT1610 Datasheet

FEATURES

■

Uses Tiny Capacitors and Inductor

■

Internally Compensated

■

Low Quiescent Current: 30µA

■

Operates with VIN 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 ModeTM Switching at Light Load

■

Low V

■

8-Lead MSOP and SO Packages

Switch: 300mV at 300mA

CESAT

U

APPLICATIO S

LT1610

1.7MHz, Single Cell
Micropower

DC/DC Converter

U

DESCRIPTIO

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 VC pin, eliminating two exter­nal 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.

■

Pagers

■

Cordless Phones

■

Battery Backup

■

LCD Bias

■

Portable Electronic Equipment

TYPICAL APPLICATIO

L1

4.7µH

65

V

IN

3

C1
22µF

SHDN

LT1610

8

V

C

1

+

1 CELL

C1, C2: AVX TAJA226M006R
D1: MOTOROLA MBR0520
L1: MURATA LQH1C4R7

Figure 1. 1-Cell to 3V Step-Up Converter

U

SW

GNDCOMP

PGND

, LTC and LT are registered trademarks of Linear Technology Corporation.

Burst Mode is a trademark of Linear Technology Corporation.

D1

R1
1M

2

FB

R2
681k

7

4

V

OUT

3V
30mA

+

C2
22µF

1610 F01

85

V

OUT

80

75

70

65

EFFICIENCY (%)

60

55

50

0.1

Efficiency

= 3V

VIN = 1.25V

VIN = 1V

1 10 100

LOAD CURRENT (mA)

VIN = 1.5V

1610 TA01

1

LT1610

1
2
3
4

8
7
6
5

TOP VIEW

V

C

FB
SHDN
PGND

COMP
GND
V

IN

SW

S8 PACKAGE

8-LEAD PLASTIC SO

WW

W

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ABSOLUTE MAXIMUM RATINGS

(Note 1)

VIN Voltage ................................................................ 8V

SW Voltage ............................................... –0.4V to 30V

FB Voltage ..................................................... VIN + 0.3V

VC Voltage ................................................................ 2V

COMP Voltage .......................................................... 2V

Current into FB Pin .............................................. ±1mA

SHDN Voltage ............................................................ 8V

U

W

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PACKAGE/ORDER INFORMATION

ORDER PART

TOP VIEW

V

1

C

2

FB

3

SHDN

4

PGND

MS8 PACKAGE

8-LEAD PLASTIC MSOP

T

= 125°C, θJA = 160°C/W

JMAX

8
7
6
5

COMP
GND
V

IN

SW

NUMBER

LT1610CMS8

MS8 PART MARKING

LTDT

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

ORDER PART

NUMBER

LT1610CS8
LT1610IS8

S8 PART MARKING

1610

T

= 125°C, θJA = 120°C/W

JMAX

1610I

Consult factory for Military grade parts.

LECTRICAL C CHARA TERIST

E

range, otherwise specifications are at T

= 25°C. Commercial grade 0°C to 70°C, V

A

ICS

The ● denotes specifications which apply over the specified temperature

= 1.5V, V

IN

= VIN, unless otherwise noted.

SHDN

(Note 2)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Operating Voltage 0.9 1 V
Maximum Operating Voltage 8V
Feedback Voltage ● 1.20 1.23 1.26 V
Quiescent Current V
Quiescent Current in Shutdown V

FB Pin Bias Current ● 27 80 nA
Reference Line Regulation 1V ≤ VIN ≤ 2V (25°C, 0°C) 0.6 1 %/V

Error Amp Transconductance ∆I = 2µA25µmhos
Error Amp Voltage Gain 100 V/V
Switching Frequency ● 1.4 1.7 2 MHz
Maximum Duty Cycle 77 80 95 %

= 1.5V, Not Switching 30 60 µA

SHDN

= 0V, VIN = 2V 0.01 0.5 µA

SHDN

= 0V, VIN = 5V 0.01 1.0 µA

V

SHDN

≤ 2V (70°C) 2 %/V

1V ≤ V

IN

2V ≤ V

≤ 8V (25°C, 0°C) 0.03 0.15 %/V

IN

≤ 8V (70°C) 0.2 %/V

2V ≤ V

IN

● 75 95 %

2

LT1610

LECTRICAL C CHARA TERIST

E

range, otherwise specifications are at T

= 25°C. Commercial grade 0°C to 70°C, V

A

ICS

The ● denotes specifications which apply over the specified temperature

= 1.5V, V

IN

= VIN, unless otherwise noted.

SHDN

(Note 2)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Switch Current Limit (Note 3) 450 600 900 mA
Switch V

CESAT

Switch Leakage Current VSW = 5V 0.01 1 µA
SHDN Input Voltage High 1V
SHDN Input Voltage Low 0.3 V
SHDN Pin Bias Current V

ISW = 300mA 300 350 mV

● 400 mV

= 3V 10 µA

SHDN

= 0V 0.01 0.1 µA

V

SHDN

The ● denotes specifications which apply over the specified temperature range, otherwise specifications are at TA = 25°C.
Industrial grade –40°C to 85°C, V

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Operating Voltage TA = 85°C 0.9 1 V

Maximum Operating Voltage 8V
Feedback Voltage ● 1.20 1.23 1.26 V
Quiescent Current 30 60 µA
Quiescent Current in Shutdown V

FB Pin Bias Current ● 27 80 nA
Reference Line Regulation 2V ≤ VIN ≤ 8V (–40°C) 0.03 0.15 %/V

Error Amp Transconductance ∆I = 2µA25µmhos
Error Amp Voltage Gain 100 V/V
Switching Frequency (Note 4) ● 1.4 1.7 2 MHz
Maximum Duty Cycle (Note 4) 77 80 95 %

Switch Current Limit 450 600 900 mA
Switch V

CESAT

Switch Leakage Current VSW = 5V 0.01 1 µA
SHDN Input Voltage High 1V
SHDN Input Voltage Low 0.3 V
SHDN Pin Bias Current V

= 1.5V, V

IN

= VIN, unless otherwise noted.

SHDN

= –40°C 1.25 V

T

A

= 0V, VIN = 2V 0.01 0.5 µA

SHDN

= 0V, VIN = 5V 0.01 1.0 µA

V

SHDN

≤ 8V (85°C) 0.2 %/V

2V ≤ V

IN

● 75 95 %

ISW = 300mA 300 350 mV

● 400 mV

= 3V 10 µA

SHDN

V

= 0V 0.01 0.1 µA

SHDN

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

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Current Limit (DC = 30%)

600

500

400

(mV)

CESAT

300

V

200

100

CESAT

0

vs Current

TA = 25°C

200 300 400

100

SWITCH CURRENT (mA)

TA = 85°C

= –40°C

T

A

500 600

1610 G01

vs Temperature

800

700

600

500

400

SWITCH CURRENT LIMIT (mA)

300

200

–50

02550

–25

TEMPERATURE (°C)

75 100

1610 G02

Current Limit vs Duty CycleV

800

700

600

500

400

300

CURRENT LIMIT (mA)

200

100

0

20 40 60 1007010 30 50 90

0

TA = 25°C

80

DUTY CYCLE (%)

1610 G03

Oscillator Frequency
vs Input Voltage Feedback Voltage

2.50
TA = 25°C

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

SWITCHING FREQUENCY (MHz)

0.25
0

0

13

2

INPUT VOLTAGE (V)

SHDN Pin Current
vs SHDN Pin Voltage

50

40

30

20

SHDN CURRENT (µA)

10

7

4

6

5

1610 G04

1.240

1.235

1.230

1.225

1.220

FEEDBACK VOLTAGE (V)

1.215

1.210

8

V

OUT

50mV/DIV

AC COUPLED

100mA/DIV

31mA

I

LOAD

1mA

–50

–25

Transient Response,
Circuit of Figure 1

I

L1

VIN = 1.25V 500µs/DIV
V

= 3V

OUT

02550

TEMPERATURE (°C)

75 100

1610 G05

1610 TA08

40

35

30

25

20

15

10

QUIESCENT CURRENT (µA)

V

OUT

20mV/DIV

AC COUPLED

SWITCH

VOLTAGE

2V/DIV

SWITCH
CURRENT
50mA/DIV

Quiescent Current
vs Temperature

5

0

–25 0 50

–50

25

TEMPERATURE (°C)

Burst Mode Operation,
Circuit of Figure 1

= 1.25V 20µs/DIV

V

IN

= 3V

V

OUT

= 3mA

I

LOAD

75

100

1610 G06

1610 TA08

4

0

0

12

SHDN VOLTAGE (V)

4

35 8

67

1610 G07

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PIN FUNCTIONS

LT1610

VC (Pin 1): Error Amplifier Output. Frequency compensa­tion 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

according to V

OUT

= 1.23V (1 + R1/R2).

OUT

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.

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BLOCK DIAGRA

V

IN

V

OUT

R1
(EXTERNAL)

R2
(EXTERNAL)

6

R5
40k

Q1

FB

2

FB

Q2
× 10

R6
40k

R3
30k

V

IN

+

A1
g

m

–

SW (Pin 5): Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to keep EMI down.

VIN (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 com­pensation.

1

V

C

COMP

8

R

C

C

C

3

SHDNSHUTDOWN

GND

7

R4
140k

+

BIAS

RAMP

GENERATOR

Σ

1.7MHz

OSCILLATOR

–

A2

+

–

COMPARATOR

Figure 2. LT1610 Block Diagram

ENABLE

FF

RQ

S

A = 3

DRIVER

+

–

5

Q3

4

SW

0.15Ω

PGND

1610 F02

5