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LTC3230

3230fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

5-LED Main/Sub Display

Driver with Dual LDO

The LTC

3230 is a low noise charge pump DC/DC converter

designed to drive 4 Main LEDs and 1 Sub LED, plus two

200mA linear regulators to provide additional system

power. The LTC3230 charge pump requires only four small

ceramic capacitors and one current set resistor to form a

complete LED power supply and current controller.

Built-in soft-start circuitry prevents excessive inrush cur-

rent during start-up and mode changes. High switching

frequency enables the use of small external capacitors.

Main and Sub full-scale current settings are programmed

by a single external resistor.

Charge pump efﬁ ciency is optimized based on the voltage

across the LED current sources. The part powers up in 1x

mode and automatically switches to the next higher mode,

1.5x and subsequently 2x, whenever any LED current

source approaches dropout.

Two 200mA linear regulators have independent enable

and output voltage select pins. Each regulator can be set

to one of three pre-selected output voltages with tri-level

input pins. The regulators may be enabled independently

of the charge pump.

The LTC3230 is available in a low proﬁ le (0.75mm) 3mm

× 3mm 20-lead QFN package.

■

Low Noise Charge Pump Provides High Efﬁ ciency

with Automatic Mode Switching

■

Multimode Operation: 1x, 1.5x, 2x

■

Full-Scale Current Set Resistor

■

Up to 125mA Total LED Current

■

Single Wire Enable/Brightness Control for Main and

Sub Display LEDs

■

32:1 Linear LED Brightness Control

■

Dual 200mA Linear Regulators

■

Four 25mA Low Dropout Main LED Current Sources

■

One 25mA Low Dropout Sub LED Current Source

■

Low Noise Constant Frequency Operation

■

Low Shutdown Current: 3μA

■

Internal Soft-Start Limits Inrush Current During

Start-Up and Mode Switching

■

Open/Short LED Protection

■

No Inductors

■

20-Lead 3mm × 3mm QFN Package

■

Multi-LED Driver and Dual LDO Supplies for Cell

Phone, PDA, Digital Camera and PND Applications

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

All other trademarks are the property of their respective owners. Protected by U.S. Patents

including 6411531.

1 F

C1P

CPO

ENM

ENS

ENLDO1

ENLDO2

SET

ENM

ENS

SET

17.4k

ENM OR ENS

MLED1

MLED2

MLED3

MLED4

SLED

LDO1

LDO2

C1M C2P

GND

SET BRIGHTNESS LEVEL ON OFF

LTC3230

C2M

125mA

MAIN SUB

1 F

3230 TA01a

1 F

1.5V

200mA

2.8V

200mA

1 F

2.2 F

= 2.7V

TO 5.5V

D1 D2 D3 D4 D5

Efﬁ ciency vs V

Voltage

(V)

EFFICIENCY (P

LED

) (%)

100

3.4

3.8

3230 TA01b

3.2

3.6

4.2

4.4

4 LEDs AT 9mA/LED

= 3V

= 25°C

Summary of content (16 pages)

PAGE 1
LTC3230 5-LED Main/Sub Display Driver with Dual LDO FEATURES DESCRIPTION ■ The LTC®3230 is a low noise charge pump DC/DC converter designed to drive 4 Main LEDs and 1 Sub LED, plus two 200mA linear regulators to provide additional system power. The LTC3230 charge pump requires only four small ceramic capacitors and one current set resistor to form a complete LED power supply and current controller.
PAGE 2
LTC3230 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Notes 1-5) VIN, CPO....................................................... –0.3V to 6V ENM, ENS, ENLDO1, ENLDO2, V1, V2, LDO1, LDO2 ......................–0.3V to (VIN + 0.3V) ICPO (Note 2) ........................................................200mA LD01, LD02 (Note 3)............................................200mA MLED1-4, SLED, RSET.................................. –0.3V to 6V Operating Ambient Temperature Range (Note 4)..........................
PAGE 3
LTC3230 ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 3.6V, C1 = C2 = C4 = C5 = C6 = 1μF, RSET = 17.4k, ENM = ENS = high, ENLDO1 = ENLDO2 = low, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS CPO Short Circuit Detection ● Threshold Voltage 0.4 1.3 V Charge Pump (CPO) 1x Mode Output Voltage ICPO = 0mA VIN V 1.5x Mode Output Voltage ICPO = 0mA 4.
PAGE 4
LTC3230 ELECTRICAL CHARACTERISTICS Note 4: The LTC3230 is guaranteed to meet performance speciﬁcations from 0°C to 85°C. Speciﬁcations over the –40°C to 85°C ambient operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125°C when overtemperature protection is active.
PAGE 5
LTC3230 TYPICAL PERFORMANCE CHARACTERISTICS 2x Mode Charge Pump Open-Loop Output Resistance vs Temperature (2VIN – VCPO)/ICPO 1.5x Mode CPO Voltage vs Load Current 12 4.8 4.2 4.0 VIN = 3.2V VIN = 3.1V VIN = 3V 3.8 10 9 8 50 100 150 LOAD CURRENT (mA) 6 –40 200 –15 10 35 TEMPERATURE (°C) 5.0 4.5 960 4.0 60 40 20 VIN CURRENT (μA) 80 TA = 85°C 940 920 TA = 25°C 900 880 TA = –40°C 860 20 15 MLED/SLED PIN CURRENT (mA) TA = –40°C 3.0 2.5 2.0 1.5 1.0 820 0.5 0 2.
PAGE 6
LTC3230 TYPICAL PERFORMANCE CHARACTERISTICS MLED/SLED Pin Current vs MLED/SLED Pin Voltage 25 VIN = 3.6V MLED/SLED CURRENT (mA) MLED/SLED PIN CURRENT (mA) 25 20 15 10 5 Efﬁciency vs VIN Voltage 90 VIN = 3.6V RSET = 17.7k 80 20 EFFICIENCY (PLED/PIN) (%) 30 MLED/SLED Current vs ENM/ENS Strobe Pulses 15 10 5 70 60 50 40 30 20 10 0 0 0.04 0.08 0.12 0.16 MLED/SLED PIN VOLTAGE (V) 0 0.20 16 8 24 NUMBER OF STROBE PULSES 0 3230 G16 2.7 0.35 0 0.30 –0.1 0.25 0.20 0.15 0.10 0.05 4.3 4.
PAGE 7
LTC3230 PIN FUNCTIONS CPO (Pin 1): Output of the Charge Pump Used to Power All LEDs. This pin is enabled or disabled using the ENM and ENS inputs. A 1μF X5R or X7R ceramic capacitor should be connected to ground. ENLDO1, ENLDO2 (Pins 2, 3): LDO1 and LDO2 Enables. Logic-level high enables LDO1 or LDO2. Logic-level low disables LDO1 or LDO2. RSET (Pin 4): LED Current Programming Resistor Pin. The RSET pin will servo to 0.8V.
PAGE 8
LTC3230 BLOCK DIAGRAM 20 17 C1P 19 C1M 16 C2M C2P GND 900kHz OSCILLATOR 18 21 VIN CPO 1 – + + 0.8V – 4 RSET TIMER ENABLE MAIN ENM 5-BIT DOWN COUNTER MLED1 7 MLED2 11 50ns FILTER 5-BIT LINEAR DAC MLED CURRENT SOURCES 8 MLED3 9 MLED4 10 TIMER 5 ENS ENABLE SUB 5-BIT DOWN COUNTER 50ns FILTER 5-BIT LINEAR DAC TIMER 3 SLED CURRENT SOURCES SLED 6 VIN SHUTDOWN ENLDO2 + – 2 + LDO1 – 12 14 ENLDO1 0.
PAGE 9
LTC3230 OPERATION Power Management The LTC3230 uses a switched capacitor charge pump to boost CPO to as much as 2 times the input voltage up to 5V. The part starts up in 1x mode. In this mode, VIN is connected directly to CPO. 1x mode provides maximum efﬁciency and minimum noise. The LTC3230 will remain in 1x mode until any LED current source drops out. Dropout occurs when a current source voltage becomes too low for the programmed current to be supplied.
PAGE 10
LTC3230 OPERATION Charge Pump Soft-Start In shutdown, CPO is disconnected from VIN and is pulled down through a 14.3k resistor. When enabled, a weak switch connects VIN to CPO. This allows VIN to slowly charge the CPO output to prevent large charging currents. The LTC3230 also employs a soft-start feature on its charge pump to prevent excessive inrush current and supply droop when switching into the step-up modes. The current available to the CPO pin is increased linearly over a typical period of 50μs.
PAGE 11
LTC3230 OPERATION charge pump function. Driving ENLDO1 and ENLDO2 high enable LDO1 and LDO2 respectively. When the charge pump is enabled, each LDO consumes an additional 60μA (typical) from VIN. If the charge pump is not enabled, one LDO consumes 125μA (typical) and the second uses 60μA (typical) additional current. The reference input to each LDO is ramped when enabled to provide an output soft-start lasting typically 100μs. When an LDO is disabled its output is pulled to ground through an 11.
PAGE 12
LTC3230 APPLICATIONS INFORMATION VIN and CPO Capacitor Selection The style and value of the capacitors used with the LTC3230 determine several important parameters such as regulator control loop stability, output ripple, charge pump strength and minimum start-up time. To reduce noise and ripple, it is recommended that low equivalent series resistance (ESR) ceramic capacitors are used on both VIN and CPO. Tantalum and aluminum capacitors are not recommended due to high ESR. times.
PAGE 13
LTC3230 APPLICATIONS INFORMATION of capacitor is needed to ensure minimum capacitances at all temperatures and voltages. • LED pads must be large and connected to the other layers of metal to ensure proper heat sinking. Table 3 shows a list of ceramic capacitor manufacturers and how to contact them. • The RSET pin is sensitive to noise and capacitance. The resistor should be placed near the part with minimum line width. Table 3. Recommended Capacitor Vendors AVX xww.avxcrp.com Kemet www.kemet.
PAGE 14
LTC3230 APPLICATIONS INFORMATION In 2x boost mode as well, the efﬁciency is similar to that of a linear regulator with an effective input voltage of 2 times the actual input voltage. In an ideal 2x charge pump, the power efﬁciency would be given by: η= PLED VLED • ILED V = = LED PIN VIN • 2 • IIN 2 • VIN Thermal Management For higher input voltages and maximum output current, there can be substantial power dissipation in the LTC3230.
PAGE 15
LTC3230 PACKAGE DESCRIPTION UD Package 20-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1720 Rev A) 0.70 ±0.05 3.50 ± 0.05 (4 SIDES) 1.65 ± 0.05 2.10 ± 0.05 PACKAGE OUTLINE 0.20 ±0.05 0.40 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3.00 ± 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD R = 0.115 TYP 0.75 ± 0.05 R = 0.05 TYP PIN 1 TOP MARK (NOTE 6) PIN 1 NOTCH R = 0.20 TYP OR 0.25 × 45° CHAMFER 19 20 0.40 ± 0.10 1 2 1.65 ± 0.
PAGE 16
LTC3230 TYPICAL APPLICATION 3-LED Main and One LED Sub at 20mA Full Scale C1 1mF VIN = 2.7V TO 5.5V C2 1mF C1P C1M C2P C2M CPO VIN C3 2.2mF MAIN C6 1mF D1 LTC3230 MLED1 MLED2 MLED3 MLED4 SLED LDO1 LDO2 ENM ENS ENM ENS ENLDO1 ENLDO2 ENLDO1 ENLDO2 V1 V2 RSET RSET 21.5k D2 SUB D3 D5 MLED4 DISABLED 1.2V 3.