National Semiconductor LM3691 Technical data

June 11, 2008

LM3691
High Accuracy, Miniature 1A, Step-Down DC-DC Converter
for Portable Applications

LM3691 High Accuracy, Miniature 1A, Step-Down DC-DC Converter for Portable Applications

General Description

The LM3691 step-down DC-DC converter is optimized for
powering ultra-low voltage circuits from a single Li-Ion cell or
3 cell NiMH/NiCd batteries. It provides up to 1A load current,
over an input voltage range from 2.3V to 5.5V. There are sev­eral different fixed voltage output options available.

LM3691 has a mode-control pin that allows the user to select
Forced PWM mode or ECO mode that changes modes be­tween gated PWM mode and PWM automatically depending
on the load. In ECO, LM3691 offers superior efficiency and
very low Iq under light load conditions. ECO mode extends the
battery life through reduction of the quiescent current during
light load conditions and system standby.

The LM3691 is available in a 6–bump micro SMD package.
Only three external surface-mount components, a 1μH induc­tor, a 4.7 μF input capacitor and a 4.7μF output capacitor, are
required.

Typical Application Circuit

Features

V

■

■

■

■

■

■

■

■

■

■

■

= 0.75V to 1.8V

OUT

±1% DC output voltage precision

2.3 ≤ VIN ≤ 5.5V
4 MHz switching frequency

64 μA (typ.) quiescent current in ECO mode
1A maximum load capability
Automatic ECO/PWM mode switching
Mode Pin to select ECO/Forced PWM mode

1 μH inductor, 4.7 μF input capacitor (0603(1608) case
size) and 4.7 μF output capacitor (0603(1608) case size)
Current overload and thermal shutdown protections

Only three tiny surface-mount external components
required (solution size less than 15 mm2)

Applications

Mobile Phones

■

Hand-Held Radios

■

MP3 players

■

Portable Hard Disk Drives

■

Efficiency vs. Output Current

(V

= 1.8V, ECO Mode)

OUT

30013430

FIGURE 1. Typical Application Circuit

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© 2008 National Semiconductor Corporation 300134 www.national.com

Connection Diagram and Package Mark Information

LM3691

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FIGURE 2. 6-Bump Thin Micro SMD Package, Large Bump

Note: The actual physical placement of the package marking will vary from part to part. The package marking “X” designates the
date code; “V” is an NSC internal code for die traceability. Both will vary in production.

NS Package Number TLA06LCA

Pin Descriptions

Pin Micro SMD Name Description

A1 EN Enable pin. The device is in shutdown mode when voltage to this pin is <0.4V and enabled

when >1.2V.
Do not leave this pin floating.

B1 Mode Mode Pin: Mode = 1, Forced PWM

Mode = 0, ECO
Do not leave this pin floating.

C1 FB Feedback analog input. Connect directly to the output filter capacitor. (Figure 1)

A2 VIN Power supply input. Connect to the input filter capacitor. (Figure 1)

B2 SW Switching node connection to the internal PFET switch and NFET synchronous rectifier.

C2 GND Ground pin.

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Ordering Information

LM3691

Voltage Option V

0.75 LM3691TL-0.75 V 250 units, Tape-and-Reel

0.85* LM3691TL-0.85 TBD 250 units, Tape-and-Reel

0.9* LM3691TL-0.9 TBD 250 units, Tape-and-Reel

1.0* LM3691TL-1.0 TBD 250 units, Tape-and-Reel

1.1* LM3691TL-1.1 TBD 250 units, Tape-and-Reel

1.2 LM3691TL–1.2 X 250 units, Tape-and-Reel

1.3* LM3691TL–1.3 TBD 250 units, Tape-and-Reel

1.375* LM3691TL–1.375 TBD 250 units, Tape-and-Reel

1.5 LM3691TL–1.5 Y 250 units, Tape-and-Reel

1.6* LM3691TL–1.6 TBD 250 units, Tape-and-Reel

1.8 LM3691TL–1.8 Z 250 units, Tape-and-Reel

* If any of the voltage options other than the released voltages are required, please contact the National Semiconductor Sales Office/Distributors for availability.

Order Number 6–bump Micro

SMD

LM3691TLX–0.75 V 3000 units, Tape-and-Reel

LM3691TLX–0.85 TBD 3000 units, Tape-and-Reel

LM3691TLX–0.9 TBD 3000 units, Tape-and-Reel

LM3691TLX–1.0 TBD 3000 units, Tape-and-Reel

LM3691TLX–1.1 TBD 3000 units, Tape-and-Reel

LM3691TLX–1.2 X 3000 units, Tape-and-Reel

LM3691TLX–1.3 TBD 3000 units, Tape-and-Reel

LM3691TLX–1.375 TBD 3000 units, Tape-and-Reel

LM3691TLX–1.5 Y 3000 units, Tape-and-Reel

LM3691TLX–1.6 TBD 3000 units, Tape-and-Reel

LM3691TLX–1.8 Z 3000 units, Tape-and-Reel

Package Marking Supplied As

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

LM3691

please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

If Military/Aerospace specified devices are required, please
contact the National Semiconductor Sales Office/Distributors
for availability and specifications.

VIN Pin to GND −0.2V to 6.0V

EN, MODE pin to GND −0.2V to 6.0V
FB, SW pin (GND−0.2V) to

Junction Temperature (T

J-MAX

Storage Temperature Range −65°C to +150°C
Continuous Power Dissipation

(Note 3)
Maximum Lead Temperature

(Soldering, 10 sec.)
ESD Rating (Note 4)
Human Body Model 2 kV
Machine Model 200V

(VIN + 0.2V) w/ 6.0V max

) +150°C

Internally Limited

260°C

Operating Ratings (Notes 1, 2)

Input Voltage Range 2.3V to 5.5V
Recommended Load Current 0 mA to 1000 mA
Junction Temperature (TJ) Range −40°C to +125°C

Ambient Temperature (TA) Range (Note5)−40°C to +85°C

Thermal Properties

Junction-to-Ambient Thermal
Resistance (θJA) (Note 6)
(micro SMD)

85°C/W

Electrical Characteristics (Notes 2, 7, 8) Limits in standard typeface are for T

= 25°C. Limits in boldface type

A

apply over the operating ambient temperature range (−30°C ≤ TA= TJ ≤ +85°C). Unless otherwise noted, specifications apply to
the LM3691 open loop Typical Application Circuit with VIN = EN = 3.6V.

Symbol Parameter Condition Min Typ Max Units

V

FB

I

SHDN

I

Q_ECO

I

Q_PWM

R

DSON (P)

R

DSON (N)

I

LIM

V

IH

V

IL

I

EN,MODE

F

SW

V

ON

Feedback Voltage PWM Mode. No load V

PWM Mode. No load V

= 1.1V to 1.8V -1 +1 %

OUT

= 0.75V to 1.0V -10 +10 mV

OUT

Shutdown Supply Current EN = 0V 0.03 1 µA

ECO Mode I

PWM Mode I

q

q

ECO Mode 64 80 µA

PWM Mode 490 600 µA

Pin-Pin Resistance for PFET VIN = VGS = 3.6V, IO = 200 mA 160 250

Pin-Pin Resistance for NFET VIN = VGS = 3.6V, IO = −200 mA 115 180

Switch Peak Current Limit Open loop 1250 1500 1700 mA

Logic High Input 1.2 V

Logic Low Input 0.4 V

Input Current 0.01 1 µA

Switching Frequency PWM Mode 3.6 4 4.4 MHz

UVLO threshold VIN rising 2.2 V

VIN falling 2.1 V

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation
of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions,
see the Electrical Characteristics tables.

Note 2: All voltages are with respect to the potential at the GND pin.

Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 150°C (typ.) and disengages at T

= 130°C (typ.).

Note 4: The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged
directly into each pin. MIL-STD-883 3015.7

Note 5: In applications where high power dissipation and/or poor package resistance is present, the maximum ambient temperature may have to be derated.
Maximum ambient temperature (T
the application (P

− (θJAx P

D-MAX

Note 6: Junction-to-ambient thermal resistance is highly application and board layout dependent. In applications where high power dissipation exists, special
care must be given to thermal dissipation issues in board design.

Note 7: Min and Max limits are guaranteed by design, test or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm.

Note 8: The parameters in the electrical characteristic table are tested under open loop conditions at VIN = 3.6V unless otherwise specified. For performance

over the input voltage range and closed loop condition, refer to the datasheet curves.

) and the junction to ambient thermal resistance of the package (θJA) in the application, as given by the following equation: T

D-MAX

). Due to the pulsed nature of testing the part, the temp in the Electrical Characteristic table is specified as TA = TJ.

) is dependent on the maximum operating junction temperature (T

A-MAX

), the maximum power dissipation of the device in

J-MAX

A-MAX

= T

mΩ

mΩ

J

J-MAX

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Block Diagram

LM3691

FIGURE 3. Simplified Functional Diagram

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Typical Performance Characteristics LM3691TL Typical Application Circuit (page 1), V

= 1.8V, TA = 25°, L = 1.0 μH, 2520, (LQM2HP1R0), CIN = C

LM3691

noted.

= 4.7 μF, 0603(1608), 6.3V, (C1608X5R0J475K) unless otherwise

OUT

= 3.6V, V

IN

OUT

Quiescent Supply current vs. Supply Voltage

No Switching (ECO Mode)

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Shutdown Current vs. Temp

(V

= 1.8V)

OUT

Quiescent Supply current vs. Supply Voltage

No Switching (PWM Mode)

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Switching Frequency vs. Temp

(V

= 1.8V, PWM Mode)

OUT

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