LM3561 [TI]

LM3561 Synchronous Boost Converter with 600mA High Side LED Driver and I 2 C-Compatible Interface; LM3561同步升压转换器600毫安高端LED驱动器和I 2 C兼容接口


型号：	LM3561
厂家：	TEXAS INSTRUMENTS
描述：	LM3561 Synchronous Boost Converter with 600mA High Side LED Driver and I 2 C-Compatible Interface LM3561同步升压转换器600毫安高端LED驱动器和I 2 C兼容接口驱动器转换器升压转换器
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中文：	中文翻译
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LM3561

LM3561 Synchronous Boost Converter with 600mA High Side LED Driver and I 2

C-Compatible Interface

Literature Number: SNOSB44B

June 21, 2011

LM3561

Synchronous Boost Converter with 600mA High Side LED

Driver and I²C-Compatible Interface

The LM3561 is available in a tiny (1.215mm × 1.615mm ×

0.6mm) 12-bump micro SMD and operates over the -40°C to

General Description

The LM3561 is a 2 MHz fixed-frequency, current mode syn-

chronous boost converter. The device is designed to operate

as a single 600mA constant current driver for high-current

white LEDs. The high side current source allows for grounded

cathode LED operation while the 250mV regulated headroom

voltage ensures that the LED current is well regulated and

efficiency remains high.

The main features of the LM3561 include: an I²C-compatible

interface for controlling the LED current, a hardware Flash

enable input for direct triggering of the Flash pulse, dual TX

inputs (TX1 and TX2) which force the Flash pulse into a low-

current Torch mode during high battery current instances, an

active high hardware enable (HWEN) allowing for fast hard-

ware shutdown during system software failures, a dual mode

pin which serves as either an indicator LED driver at up to

18mA or as a dedicated comparator input with an internal 1V

reference, designed to monitor the voltage across a negative

+85°C temperature range.

Features

High Side Current Source allowing for Grounded LED

Cathode

■

Up to 90% Efficient

Ultra-Small Solution Size: < 16mm²

■

Three Operating Modes: Torch, Flash, and LED Indicator

Accurate and Programmable LED Current from 18mA to

600mA

Hardware Flash and Torch Enable

■

LED Thermal Sensing and Current Scaleback

Software Selectable Input Voltage Monitor

Programmable Flash Timeout

Dual Synchronization Inputs for RF Power Amplifier Pulse

Events

■

temperature coefficient thermistor (NTC), and

a pro-

grammable input voltage monitor which monitors IN and can

reduce the flash current or shutdown the device during low

battery conditions.

Open and Short LED Detection

■

Active High Hardware Enable for Protection Against

System Faults

Seven fault flags are available for read back over the I²C-

compatible bus. These include: a flash timeout flag indicating

the flash pulse has reached the end of the programmable

timeout duration, a thermal shutdown flag indicating the

LM3561's die temperature has exceeded 150°C, an LED fault

flag indicating the output voltage has tripped the over-voltage

threshold, or the LED has become shorted, TX1 and TX2 in-

terrupt flags indicating if either of the TX inputs have been

triggered, an NTC flag indicating the LED has experienced an

over temperature condition, and a VIN Monitor flag indicating

the input voltage has fallen below the VIN Monitor threshold.

400kHz I²C-compatible Interface

■

12-Bump (1.215mm × 1.615mm × 0.6mm) micro SMD

Applications

Camera Phone LED Flash Controller

■

LED Current Source Biasing

Typical Application Circuits

30113902

Example Layout

30113901

301139

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Application Circuit Component List

Component

Manufacturer

TDK

Value

1µH

Part Number

MLP2520-1R0

Size (mm)

2x2.5x1.2

Rating

1.5A

COUT

CIN

Murata

10µF

GRM188R60J106M

LXCL-PWF4

1.6×0.8×0.8 (0603)

6.3V

Murata

10µF

6.3V

LEDs

Lumiled

3.6V@1A

1.5A

Connection Diagram

30113903

Pin Descriptions

Name

GND

Function

Ground

Input Voltage Connection. Connect IN to the input supply and bypass to GND with a minimum

10µF ceramic capacitor.

HWEN

Active Low Hardware Reset Input. This input is high impedance and cannot be left floating.

Typically this would be tied to a pullup resistor and to a logic high voltage, or VIN, in order to enable

the LM3561.

Drain Connection for Internal NMOS and Synchronous PMOS Switches

Active High Hardware Flash Enable. Drive STROBE high to turn on the Flash pulse. STROBE has

an internal 300kΩ pulldown to GND.

STROBE

SCL

OUT

Serial Clock Input.

Step-Up DC/DC Converter Output. Bypass OUT to GND with a 10µF Ceramic Capacitor.

Configurable as a Flash Interrupt Input, a Hardware Torch Enable, or a Programmable General

Purpose Logic Input/Output. This pin has an internal 300kΩ pulldown to GND.

Serial Data Input/Output.

TX1/TORCH/

GPIO

SDA

LED

High Side Current Source Output for Flash LED.

Configurable as a High Side Current Source Output for Indicator LEDs or as a Threshold Detector

for LED Temperature Sensing.

LEDI/NTC

Configurable as a Flash Interrupt Input, a Programmable General Purpose Logic Input/Output, or

TX2/GPIO2/INT

as an Interrupt output for fault notification. This pin has an internal 300kΩ pulldown to GND.

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Ordering Information

Top Marking

2 Lines: First line XY, where X is the

single digit date code and Y is the die

run code, Second line has the letters

Order Number

Package

Supplied As

No-Lead

LM3561TME

LM3561TMX

TMD12AAA

250 units, Tape-and-Reel

3000 units, Tape-and-Reel

YES (NOPB)

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Absolute Maximum Ratings (Note 1, Note

Operating Ratings (Note 1, Note 2)

V_IN

2.5V to 5.5V

-40°C to +125°C

-40°C to +85°C

Junction Temperature (T_J)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Ambient Temperature (T_A)

(Note 5)

V_IN, V_SW, V_OUT

-0.3V to 6V

Thermal Properties

Junction-to-Ambient Thermal

Resistance (θ_JA), TMD12

Package(Note 6)

V_SCL, V_SDA, V_HWEN, V_STROBE, V_TX1

V_TX2, V_LED, V_LEDI/NTC

-0.3V to (V_IN

+0.3V) w/ 6.0V

max

68°C/W

Continuous Power Dissipation(Note 3) Internally Limited

Junction Temperature (T_J-MAX

)

+150°C

Storage Temperature Range

-65°C to +150°C

Maximum Lead Temperature

(Soldering)

(Note 4)

ESD Caution Notice National Semiconductor recommends that all integrated circuits be handled with appropriate

ESD precautions. Failure to observe proper ESD handling techniques can result in damage to the device.

Electrical Characteristics

Limits in standard typeface are for T_A= +25°C. Limits in boldface type apply over the full operating ambient temperature range

(-40°C ≤ T_A≤ +85ºC). Unless otherwise specified, V_IN= 3.6V, V_HWEN= V_IN. (Note 2, Note 7)

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Current Source Specifications

600mA Flash LED

Setting, V_OUT= 4.5V,

-40C ≤ T_A≤

+85C

-5%

-3%

600

+6%

3V ≤ V_IN≤ 4.2V

18mA Torch Current Setting, V_OUT= 4.5V,

T_A= +25C

I_LED

Current Source Accuracy

Current Source Regulation

-10%

+10%

3V ≤ V_IN≤ 4.2V

V_HR

600mA setting, V_OUT= 4.5V

240

Voltage (V_OUT- V_LED

)

Step-Up DC/DC Converter Specifications

Output Over-Voltage

Protection Trip Point(Note

On Threshold

4.90

5.05

V_OVP

Off Threshold

4.88

PMOS Switch On-

Resistance

R_PMOS

R_NMOS

I_PMOS= 500mA

I_NMOS= 500mA

270

250

mΩ

NMOS Switch On-

Resistance

Flash Duration

3.0V ≤ V_IN≤ 4.2V

Flash Duration

0.88

1.35

1.12

1.65

Switch Current Limit(Note

I_CL

'1'

1.5

Output Short Circuit

Current Limit

I_{OUT_SC}

I_LED/NTC

V_TRIP

V_OUT< 2.3V

200

Indicator Register = 0xFF, V_LEDI/NTC= 2V,

2.7V ≤ V_IN≤ 4.2V

Indicator Current

Configuration Register 1 Bit [4] = '1', 3.0V

Comparator Trip Threshold

Switching Frequency

Timeout Duration

0.97

1.8

1.03

2.2

MHz

≤ V_IN≤ 4.2V

f_SW

2.7V ≤ V_IN≤ 5.5V

t_TIMEOUT(Note

10), (Note 11)

-10

+10

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Symbol

Parameter

Conditions

Device Not Switching

Min

Typ

676

Max

Units

Quiescent Supply Current

into IN

I_Q

Device Switching

1140

560

µA

Indicate Mode, Indicator Register = 0x07

I_SHDN

I_STBY

Shutdown Supply Current

Standby Supply Current

0.02

µA

2.7V ≤ V_IN≤ 5.5V, HWEN = GND

2.7V ≤ V_IN≤ 5.5V, HWEN = IN, Enable

1.1

2.3

TX_ Low-to-High, I_LED= 600mA to

93.2mA

Flash-to-Torch LED

Current Settling Time

t_TX

µs

TX_ Low-to-High, I_LED= 93.2mA to

600mA

Torch-to-Flash LED

Current Settling Time

V_INFalling, VIN Monitor Register = 0x01

(Enabled with V_{IN_TH}= 2.9V)

V_{IN_TH}

VIN Monitor Trip Threshold

2.84

2.90

2.95

HWEN, STROBE, TX1/TORCH/GPIO1, TX2/INT/GPIO2 Voltage Specifications

V_IL

V_IH

Input Logic Low

Input Logic High

0.4

V_IN

2.7V ≤ V_IN≤ 5.5V

1.2

Output Logic Low

(GPIO1,GPIO2, INT)

V_OL

0.4

I_LOAD= 3mA, 2.7V ≤ V_IN≤ 5.5V

Internal Pulldown

Resistance at TX1/

TORCH/GPIO1

R_TX1

300

kΩ

Internal Pulldown

Resistance at TX2/GPIO2

R_TX2

300

kΩ

Internal Pulldown

Resistance at STROBE

R_STROBE

I²C-Compatible Voltage Specifications (SCL, SDA)

V_IL

V_IH

V_OL

Input Logic Low

0.4

V_IN

2.7V ≤ V_IN≤ 5.5V

Input Logic High

1.3

2.7V ≤ V_IN≤ 5.5V

Output Logic Low (SDA)

400

I_LOAD= 3mA, 2.7V ≤ V_IN≤ 5.5V

I²C-Compatible Timing Specifications (SCL, SDA) (Note 10) see Figure 1

f_SCL

SCL(Clock Frequency)

400

300

kHz

20 + 0.1 ×

C_BUS

Rise Time of Both SDA and

SCL

t_{RISE(Note 12)}

20 + 0.1 ×

C_BUS

Fall Time of Both SDA and

SCL

t_{FALL(Note 12)}

300

t_LOW

t_HIGH

Low Period of SCL Clock

High Period of SCL Clock

1.3

µs

600

Hold Time for Start (or

Repeated Start) Condition

t_HD;STA

t_SU;STA

600

Set-up Time for a Repeated

Start

t_HD;DAT

t_SU;DAT

Data Hold Time

Data Setup Time

100

Set-up Time for Stop

Condition

t_SU;STO

t_VD;DAT

t_VD;ACK

600

Data Valid Time

900

Data Valid Acknowledge

Time

Bus Free Time Between a

Start and a Stop Condition

t_BUF

1.3

µs

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Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device 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 table.

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 T_J=150ºC (typ.) and disengages at

T_J=135ºC (typ.).

Note 4: For detailed soldering specifications and information, please refer to National Semiconductor Application Note 1112: Micro SMD Wafer Level chip Scale

Package (AN-1112)

Note 5: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be

derated. Maximum ambient temperature (T_A-MAX) is dependent on the maximum operating junction temperature (T_J-MAX-OP= +125ºC), the maximum power

dissipation of the device in the application (P_D-MAX), and the junction-to-ambient thermal resistance of the part/package in the application (θ_JA), as given by the

following equation: T_A-MAX= T_J-MAX-OP– (θ_JA× P_D-MAX).

Note 6: Junction-to-ambient thermal resistance (θ_JA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the

JEDEC standard JESD51-7. The test board is a 4-layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2x1 array of thermal via's. The ground plane on

the board is 50mm x 50mm. Thickness of copper layers are 36µm/18µm/18µm/36µm (1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22°C, still air.

Power dissipation is 1W.

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

norm. Unless otherwise specified, conditions for typical specifications are: V_IN= 3.6V and T_A= +25°C.

Note 8: The typical curve for Over-Voltage Protection (OVP) is measured in closed loop using the typical application circuit . The OVP value is found by forcing

an open circuit in the LED current path and recording the peak value of V_OUT. The value given in the Electrical Table is found in an open loop configuration by

ramping the voltage at OUT until the OVP comparator trips. The closed loop data can appear higher due to the stored energy in the inductor being dumped into

the output capacitor after the OVP comparator trips. This results in an open circuit condition where the output voltage can continue to rise after the OVP comparator

trips by approximately I_IN×sqrt(L/C_OUT).

Note 9: The typical curve for Current Limit is measured in closed loop using the typical application circuit by increasing I_OUTuntil the peak inductor current stops

increasing. The value given in the Electrical Table is measured open loop and is found by forcing current into SW until the current limit comparator threshold is

reached. Closed loop data appears higher due to the delay between the comparator trip point and the NFET turning off. This delay allows the closed loop inductor

current to ramp higher after the trip point by approximately 40ns × V_IN/L

Note 10: Guaranteed by design. Not production tested.

Note 11: The timeout duration period is a divided down representation of the 2MHz clock and thus the accuracy spec. is the same as the switching frequency.

This accuracy spec. applies to all settings in Table 8.

Note 12: Min rise and fall times on SDA and SCL can typically be less than 20ns.

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I²C Timing

301139119

FIGURE 1. I²C Timing

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Typical Performance Characteristics V_IN= 3.6V, LEDs are Lumiled PWF-4, C_OUT= 10µF, C_IN= 10µF,

L = MLP2520-1R0 (1µH, R_L= 0.085Ω), T_A= +25°C unless otherwise specified.

LED Efficiency vs V_IN

Flash Brightness Codes (1111 - 1100)

(Typical Application Circuit)

LED Efficiency vs V_IN

Flash Brightness Codes (1011 - 1000)

(Typical Application Circuit)

30113954

30113953

LED Efficiency vs V_IN

Flash Brightness Codes (0111 - 0100)

(Typical Application Circuit)

LED Efficiency vs V_IN

Flash Brightness Codes (0011 - 0000)

(Typical Application Circuit)

30113952

30113951

LED Current vs V_IN

Flash Brightness Codes (1111 - 1100)

LED Current vs V_IN

Flash Brightness Codes (1011 - 1000)

30113950

30113949

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LED Current vs V_IN

Flash Brightness Codes (0111 - 0100)

LED Current vs V_IN

Flash Brightness Codes (0011 - 0000)

30113948

30113947

Shutdown Current vs V_IN

( V_HWEN= GND)

Shutdown Current vs V_IN

( V_HWEN= V_IN)

30113957

30113958

Indicator Current vs Headroom Voltage (VIN - VLED)

Indicator Brightness Codes (111 - 100)

Indicator Current vs Headroom Voltage (VIN - VLED)

Indicator Brightness Codes (011 - 000)

30113956

30113955

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Startup into Flash Mode

Max Flash Setting

Torch Mode to Flash Mode Transition

Torch Brightness Code (100)

Flash Brightness Code (111)

30113961

30113963

TX Interrupt Operation

Torch Brightness Code (100)

Flash Brightness Code (111)

Line Transient

Flash Brightness Code (111)

30113962

30113960

HWEN Operation

NTC Mode Response

Flash Brightness Code (111)

Circuit of Figure 15

(R(T) = 10kΩ (@+25°C), RBIAS = 1.3kΩ, VBIAS = 1.2V)

30113959

30113965

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V_INMonitor Response

Flash Brightness Code (111)

3.0V Setting

30113964

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Block Diagram

30113905

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Mode. If the difference between V_OUTand V_LEDis greater than

250mV, the device will operate in Pass Mode. In Pass Mode

the boost converter stops switching and the synchronous

Circuit Description

OVERVIEW

PFET turns fully on, bringing V_OUTup to (V_IN– I_IN×R_PMOS

)

The LM3561 is a high power white LED flash driver capable

of delivering up to 600mA of LED current into a single white

LED. The device incorporates a 2MHz constant frequency,

synchronous boost converter, and a high side current source

to regulate the LED current over the 2.5V to 5.5V input voltage

range.

where (R_PMOS= 240mΩ). In Pass Mode the inductor current

is not limited by the peak current limit. In this situation the

output current must be limited to 1.5A.

OVER-VOLTAGE PROTECTION

The output voltage is limited to typically 5V (4.9V min). In sit-

uations such as the current source open, the LM3561 will

raise the output voltage in order to try and keep the LED cur-

rent at its target value. When V_OUTreaches 5V, the over-

voltage comparator will trip and turn off both the internal NFET

and PFET switches. When V_OUTfalls below 4.8V (typical) the

LM3561 will begin switching again.

When the LM3561 is enabled and the output voltage is greater

than V_IN– 150mV, the PWM converter switches and main-

tains at least 250mV (V_HR) across the current source (V_OUT

V_LED). This minimum headroom voltage ensures that the

current sinks remain in regulation. When the input voltage is

above V_LED+ V_HRthe device operates in pass mode with the

device not switching and the PFET on continuously. In pass

mode the difference between (V_IN- I_LED×R_{ON_P}) and V_LEDis

dropped across the current source. If the device is operating

in pass mode and V_INdrops to a point that forces the device

into switching, the LM3561 will make a one-time decision to

jump into switching mode. The LM3561 remains in switching

mode until the device is shutdown and re-enabled. This is true

even if V_INwere to rise back above V_LED+ 250mV during the

active Flash or Torch cycle. This prevents the LED current

from oscillating back and forth between pass and boost mode

CURRENT LIMIT

The LM3561 features 2 selectable current limits — 1A and

1.5A. These are selectable through the I²C-compatible inter-

face via bit [5] of the Flash Duration Register. When the

current limit is reached the LM3561 stops switching for the

remainder of the switching cycle.

Since the current limit is sensed in the NMOS switch there is

no mechanism to limit the current when the device operates

in Pass Mode. In situations where there could potentially be

large load currents at OUT, and the LM3561 is operating in

Pass mode, the load current must be limited to 1.5A. In Boost

mode or Pass mode if V_OUTfalls below approximately 2.3V

the part stops switching and the PFET operates as a current

source limiting the current to typically 200mA. This prevents

damage to the LM3561 and excessive current draw from the

battery during output short circuit conditions.

when V_INis close to V_OUT

The main features of the LM3561 include: dual TX inputs (TX1

and TX2) for forcing the device into a lower current state dur-

ing high battery current conditions, a hardware flash enable

input (STROBE), an active low shutdown input (HWEN), an

input voltage monitor for detecting low battery voltage condi-

tions, and a dual function pin that can be configured as a low

power indicator LED current source or as a comparator input

for LED thermal sensing via an external NTC thermistor.

THERMAL SHUTDOWN

The LM3561 features a thermal shutdown threshold of typi-

cally +150°C. When the die temperature reaches +150°C, the

active current source (LED) will shutdown, and the TSD flag

in the Flags register is written high. The device cannot be

started up again until the Flags register is read back. Once

the Flags register is read back the current source can be re-

enabled into Torch, or Flash Mode. The thermal shutdown

(TSD) circuitry has an internal 250µs de-glitch timer which

helps prevent unwanted noise from falsely triggering a TSD

event. However, when the LM3561 is in boost mode at higher

flash currents, the de-glitch timer can get reset by the high

currents in the LM3561's GND. As a result the thermal

shutdown's internal de-glitch timer can get reset before the

TSD event can get latched in. This causes a TSD event to not

get triggered until the LM3561's flash pulse reaches the end

of the flash duration, when the noisy currents have dropped

to a lower level. However, once the noise is lower and a TSD

event is triggered, the next flash pulse is not allowed until the

flags register is read back. In pass mode the boost switcher

is off and the lower noise environment allows the devices TSD

circuitry to shutdown immediately when the die temperature

reaches +150°C.

Control of the LM3561 is done via an I²C-compatible inter-

face. This includes: adjustment of the LED current in TORCH

and FLASH mode, adjustment of the indicator LED current,

programming the flash LED current timeout duration, and

programming of the switch current limit. Additionally, there are

7 flag bits that can be read back indicating that the pro-

grammed flash current timeout has expired, a device over

temperature condition has happened, an LED failure (open or

short), an LED thermal failure (tripping of the internal NTC

comparator), an input under voltage fault (VIN Monitor), and

a separate flag for each TX input.

STARTUP

Turn on of the LM3561 via the I²C-compatible interface is

done through bits [1:0] of the Enable Register. The device can

be enabled in either Indicate mode, Torch mode, or Flash

mode (see Table 2). On startup in Flash or Torch mode, when

V_OUTis less than V_IN, the internal synchronous PFET turns on

as a current source and delivers typically 200mA to the output

capacitor. During this time the flash LED current source (LED)

is off. When the voltage across the output capacitor reaches

2.3V the current source can turn on. At turn-on, the current

source steps through each FLASH and TORCH level until the

target LED current is reached (32µs/step). This gives the de-

vice a controlled turn-on and limits inrush current from the

V_INsupply.

FLASH MODE

In Flash mode the LED current source (LED) provides 16 dif-

ferent current levels from typically 36mA to 600mA. The Flash

currents are set by writing to bits [3:0] of the Flash Brightness

Resister. Flash mode is activated by either writing a (1, 1) to

bits [1:0] of the Enable Register, or by pulling the STROBE

pin high. Once the Flash sequence is activated the current

source (LED) will ramp up to the programmed Flash current

PASS MODE

On turn on, when the output voltage charges up to ( V_IN– 150

mV), the LM3561 will decide if the part operates in Pass Mode

or Boost mode. If the voltage difference between V_OUTand

V_LEDis less than 250mV, the device will transition into Boost

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by stepping through all Torch and Flash levels (32µs/step)

until the programmed current is reached.

Hardware Torch Mode

With Configuration Register 1 Bit [7] = '1', TX1/TORCH/

GPIO1 is configured as a hardware Torch mode enable. In

this mode (TORCH mode), a high at TORCH turns on the LED

current at the programmed Torch current setting. The

STROBE input and I²C Enabled flash take precedence over

TORCH mode. In hardware torch mode, both the LED current

source will turn off after a flash event and Configuration Reg-

ister 1 Bit [7] will be reset to '0'. In this situation, to re-enter

torch mode via hardware torch, the hardware torch enable bit

(Configuration Register 1 Bit [7] must be reset to '1'). , , and

detail the functionality of the TX1/TORCH input.

FLASH TERMINATION

Bit [2] of the Enable Register determines how the Flash pulse

terminates. With this bit = '1' the Flash current pulse will only

terminate by reaching the end of the Flash timeout period (see

Figure 6). With STR = '0', Flash mode can be terminated by

pulling STROBE low, programming bits [1:0] of the Enable

elapse (see Figure 5). If STR = '0' and STROBE is toggled

before the end of the Flash timeout period, the timeout period

resets on the rising edge of STROBE. See LM3561 Timing

Diagrams regarding the Flash pulse termination for the dif-

ferent STR bit settings.

GPIO1 Mode

With GPIO Register bit[0] = '1', the TX1/TORCH/GPIO1 pin is

configured as a general purpose I/O. In GPIO1 mode this pin

can be either a logic input or a logic output depending on the

bit settings in bits [2:1] of the GPIO Register (see Table 4).

After the Flash pulse terminates, either by a flash timeout,

pulling STROBE low, or disabling it via the I²C-compatible in-

terface, the current source (LED) turns completely off. This

happens even when Torch is enabled via the I²C-compatible

interface and the Flash pulse is turned on by toggling

STROBE. After a Flash event ends (bits [1:0] of the Enable

FLASH PULSE INTERRUPT (TX2), GENERAL PURPOSE

I/O (GPIO2), AND INTERRUPT OUTPUT (INT)

The TX2/GPIO2/INT pin has a triple function: either a flash

interrupt input (TX2), a general purpose I/O (GPIO2), or as an

interrupt output (INT).

FLASH TIMEOUT

The Flash timeout period sets the maximum duration of the

flash current pulse. Bits [4:0] of the Flash Duration Register

programs the 32 different Flash timeout levels in steps of

32ms, giving a Flash timeout range of 32ms to 1024ms (see

Table 8).

Flash Interrupt (TX2 Mode)

In TX2 mode (default), TX2 is a flash pulse interrupt input.

This is designed to force the flash pulse into a lower current

state in order to reduce the current pulled from the battery

during high battery current situations. For example, when the

LM3561 is engaged in a Flash event, and TX2 is pulled high

(active high polarity, the current source (LED) is forced into

torch mode at the programmed Torch current setting. If TX2

is then pulled low before the flash pulse terminates, the LED

current will step back to the previous flash current level. At the

end of the flash timeout, whether the TX2 pin is high or low,

the LED current will turn off. In addition to forcing torch mode

with a TX2 event, the TX2 input can be set to force shutdown.

Configuration Register 2 bit[0] sets this mode (see Table

11). In TX2 shutdown mode, a TX2 event will shut down the

flash pulse. Once shut down, the flash pulse must be re-en-

abled via STROBE or the flash enable bits in the Enable

TORCH MODE

In Torch mode the current source (LED) provides 8 different

current levels (see Table 6). The Torch currents are adjusted

by writing to bits [2:0] of the Torch Brightness Register. Torch

mode is activated by setting Enable Register bits [1:0] to (1,

0). Once the Torch mode is enabled the current sources will

ramp up to the programmed Torch current level by stepping

through all of the Torch currents at (32µs/step) until the pro-

grammed Torch current level is reached.

FLASH PULSE INTERRUPT (TX1), HARDWARE TORCH

INPUT (TORCH) AND GENERAL PURPOSE I/O (GPIO1)

The TX1/TORCH/GPIO1 input has a triple function; either as

a flash pulse interrupt (TX1), a hardware torch mode enable

(TORCH), or as a general purpose I/O (GPIO1).

TX2 Forcing Shutdown

TX2 also has the capability to force shutdown (see Figure 7).

When bit [0] of Configuration Register 2 is set to a '1', TX2 will

force shutdown when active. For example, if TX2 is config-

ured for TX2 mode with active high polarity, and bit [0] of

Configuration Register 2 is set to '1' then when TX2 is driven

high, (LED) will be forced into shutdown. Once the current

source is forced into shutdown by activating TX2, the current

source can only be re-enabled in flash mode if TX2 is pulled

low, and the Flags register is read back. If only the Flags reg-

ister is read back and TX2 is kept high, the device will be re-

enabled into torch mode and not shutdown. This occurs

because the TX2 shutdown feature is an edge-triggered

event. With active high polarity the TX2 shutdown requires a

rising edge at TX2 in order to force the current source back

into shutdown. Once shut down, it takes a read back of the

flags Register and another rising edge at TX2 to force shut

down again.

Flash Interrupt (TX1)

With Configuration Register 1 Bit [7] = '0' (default), TX1/

TORCH/GPIO1 is a flash pulse interrupt input. This is de-

signed to force the flash pulse into a lower current state in

order to reduce the current pulled from the battery during high

battery current situations. For example, when the LM3561 is

engaged in a Flash event and TX1 is pulled high (active high

polarity) the current source (LED) is forced into Torch mode

at the programmed Torch current setting. If TX1 is then pulled

low before the Flash pulse terminates, the LED current will

ramp back to the previous Flash current level. At the end of

the Flash timeout, whether TX1 is high or low, the LED current

will turn off.

TX1 Polarity

In TX1 mode, TX1 can be programmed as an active low TX1

input where pulling TX1 to GND will cause a TX1 event. TX1

polarity inversion is done via Configuration Register 1 bit [5].

TX2 Polarity

In TX2 mode (default), TX2 is a flash pulse interrupt input.

This is designed to force the flash pulse into a lower current

state in order to reduce the current pulled from the battery

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during high battery current situations. For example, when the

LM3561 is engaged in a Flash event and TX2 is pulled high

(active high polarity) the current source (LED) is forced into

torch mode at the programmed Torch current setting. If TX2

is then pulled low before the flash pulse terminates, the LED

current will step back to the previous flash current level. At the

end of the flash timeout, whether the TX2 pin is high or low,

the LED current will turn off. In addition to forcing torch mode

with a TX2 event, the TX2 input can be set to force shutdown.

Configuration Register 2 bit[0] sets this mode (see Figure 8).

In TX2 shutdown mode, a TX2 event will shutdown the flash

pulse. Once shut down, the flash pulse must be re-enabled

via STROBE or the flash enable bits in the Enable Register.

V_TRIP. With Configuration Register 2 bit [1] = '1' the device will

shut down the current source (LED) when V_LEDI/NTCfalls be-

low V_TRIP. When the LM3561 is forced from Flash to Torch,

normal LED operation (during the same Flash pulse) can only

be re-started by reading from the Flags Register and ensuring

the voltage at V_LEDI/NTCis above V_TRIP. When V_LEDI/NTCfalls

below V_TRIPand the Flags register is cleared, the LM3561 will

go through a 250µs deglitch time before the flash current falls

to either torch mode or goes into shutdown. This deglitch time

prevents noise from inadvertently tripping the NTC compara-

tor. For a more detailed description of this mode and design-

ing the NTC circuit (see NTC THERMISTOR SELECTION

section in the Applications Information section of this

datasheet).

GPIO2 Mode

In NTC mode the NTC flag (see Flags Register and Fault In-

dicators section) can be output on the TX2/GPIO2/INT pin.

This is accomplished by making the TX2/GPIO2/INT an in-

terrupt output (see Interrupt Output Mode section).

The TX2/GPIO2/INT pin is configured as a general purpose

logic input/output by setting GPIO Register bit[3] = '1'. In

GPIO2 mode this pin can be either a logic input or output de-

pending on the bit settings for GPIO Register bit [4] (see Table

4).

ALTERNATE EXTERNAL TORCH (AET MODE)

With Configuration Register 2 bit [2] set to '1' the operation of

TX1/TORCH becomes dependent on its occurrence relative

to STROBE. In this mode if TX1/TORCH goes high first, fol-

lowed by STROBE going high, the LEDs are forced into torch

mode with no timeout. In this mode if TX1/TORCH goes high

after STROBE has gone high, then the TX1/TORCH pin op-

erates as a normal flash interrupt, and the LEDs will turn off

at the end of the timeout duration. (See LM3561 Timing Dia-

grams: Figure 9 and Figure 10). AET mode is can only be

used with STROBE configured as a level sensitive input.

Configuring STROBE for edge sensitive operation (STR bit =

1), will force TX1 to act as a simple flash interrupt.

Interrupt Output Mode

The TX2/GPIO2/INT pin is configured as an interrupt output

by setting the TX2/GPIO2/INT as a GPIO output and setting

bit [6] of the GPIO register to '1'. When in INT mode, the TX2/

GPIO2/INT pin will pull low when either of the following occur:

1. The LM3561 is in NTC Mode, the LED current source is

enabled, and V_NTCfalls below V_TRIP

2. The LM3561's Input Voltage Monitor is enabled and V_IN

falls below V_{IN_TH}

INDICATOR LED/THERMISTOR (LEDI/NTC)

The LEDI/NTC pin serves a dual function, either as an LED

indicator driver or as a threshold detector for a negative tem-

perature coefficient (NTC) thermistor circuit.

INPUT VOLTAGE MONITOR

The LM3561 has an internal comparator that monitors the

voltage at IN and can force the LED current into torch mode

or into shutdown if V_INfalls below the programmable VIN

Monitor Threshold (V_{IN_TH}). Bit [0] in the VIN Monitor register

enables or disables this feature. When enabled, Bits [2:1]

program the 4 adjustable thresholds of 2.9V, 3V, 3.1V, and

3.2V. Bit [3] in Configuration Register 2 selects whether an

under-voltage event forces Torch mode or forces the LED

current source off. (See Table 5 and Table 11.)

Led Indicator Mode (LEDI)

LEDI/NTC is configured as an LED indicator driver by setting

Configuration Register 1 bit [4] = '0' (default). The indicator

current source is enabled by setting Enable Register bits [1:0]

= '01'. In Indicator mode there are 8 different current levels

available (2.25mA - 18mA) which are programmed through

the Indicator Register (see Table 3).

When the VIN Monitor is active and V_INfalls below the pro-

grammed threshold (V_{IN_TH}) the LEDs will either turn off or

their current will be reduced to the programmed Torch current

setting. To reset the LED current to its previous level, two

things must occur. First, V_INmust go above V_{IN_TH,}and the

Flags register must be read back.

Led Thermal Comparator (NTC Mode)

Writing a '1' to Configuration Register 1 bit [4] disables the

indicator current source and configures LEDI/NTC as a com-

parator input for monitoring an NTC thermistor circuit. In this

mode LEDI/NTC becomes the negative input of an internal

comparator, with the positive input internally connected to an

internal reference (V_TRIP= 1V). Additionally, Configuration

voltage at LEDI/NTC falls below V_TRIP. With Configuration

into Torch mode when the voltage at LEDI/NTC falls below

In VIN Monitor mode the VIN Monitor Flag (see Flags Register

and Fault Indicators section) can be output on the TX2/

GPIO2/INT pin. This is accomplished by making the TX2/

GPIO2/INT an interrupt output (see Interrupt Output Mode

section).

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LM3561 Timing Diagrams

30113937

FIGURE 2. Torch to Flash Operation

30113938

FIGURE 3. TX Event During a Flash Pulse (TX1/TORCH is an Active High TX Input)

30113939

FIGURE 4. TX Event Before and After a Flash Event (TX1/TORCH is an Active High TX Input)

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30113940

FIGURE 5. STROBE Input is Level Sensitive (Enable Register Bit [2] = '0')

30113941

FIGURE 6. STROBE Input is Edge Sensitive (Enable Register Bit [2] = '1')

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30113942

FIGURE 7. TX2 Configured as an Active High Flash Interrupt and Set to Force Shutdown

30113943

FIGURE 8. TX2 Configured as an Active Low TX Input and Set to Force Torch Mode

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30113944

FIGURE 9. Alternate External Torch Mode

(TX1/TORCH Turns on Before STROBE; when TX1/TORCH goes low, Flash mode is initiated)

30113945

FIGURE 10. Alternative External Torch Mode

(STROBE Goes High Before TX1/TORCH, Same as Normal TX1 Operation)

30113946

FIGURE 11. TX1/TORCH Pin is Configured as a Hardware Torch Input

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LED short threshold of 500mV (typical) to when the fault flag

is valid. There is a 2µs delay from when the LEDF flag is valid

on an LED open. This delay is the time between when the

OVP threshold is triggered and when the fault flag is valid.

The LEDF flag can only be reset to (0) by pulling HWEN low,

removing power to the LM3561, or reading the Flags Register.

Flags Register and Fault Indicators

The Flags Register contains the Interrupt and Fault indicators.

Seven flags are available in the Flags Register. These include

a Flash Timeout flag (TO), a Thermal Shutdown flag (TSD) ,

an LED Failure flag (LEDF) , an LED Thermal flag (NTC), and

a VIN Monitor flag. Additionally, two interrupt flag bits TX1

interrupt and TX2 interrupt indicate a change of state of the

TX1/TORCH pin (TX1 mode) and TX2/GPIO2/INT pin (TX2

mode) . Reading back a '1' indicates the TX lines have

changed state since the last read of the Flags Register. A read

of the Flags Register resets the flag bits.

LED THERMAL FAULT

The NTC flag (bit [5] of the Flags Register) reads back a '1' if

the LM3561 is active in Flash or Torch mode, the device is in

NTC mode, and the voltage at LEDI/NTC has fallen below

V_TRIP(1V typical). When this has happened and the LM3561

has been forced into Torch or LED shutdown, depending on

the state of Configuration Register 2 bit [1], the voltage at LE-

DI/NTC must rise above the V_TRIPthreshold and the Flags

normal operation. (see Led Thermal Comparator (NTC

Mode) section for more details).

FLASH TIMEOUT

The Flash Timeout Flag (TO), (bit [0] of the Flags Register)

reads back a '1' if the LM3561 is active in Flash Mode and the

timeout period expires before the flash pulse is terminated.

The flash pulse can be terminated before the timeout period

expires by pulling the STROBE pin low (with STR bit '0'), or

by writing a ‘0’ to bits [1:0] of the Enable Register. The TO flag

is reset to (0) by pulling HWEN low, removing power to the

LM3561, reading the Flags Register, or when the next Flash

pulse is triggered.

INPUT VOLTAGE MONITOR FAULT

The V_INMonitor Flag (bit [7] of the Flags Register) reads back

a '1' when the Input Voltage Monitor is enabled and V_INfalls

below the programmed (V_{IN_TH}). The input voltage must rise

above V_{IN_TH}and the Flags register must be read back in or-

der to resume normal operation after the LED current has

been forced to Torch mode or turned off due to a VIN Monitor

event.

THERMAL SHUTDOWN

When the LM3561’s die temperature reaches +150°C the

boost converter shuts down and the NFET and PFET turn off.

Additionally, both current sources (LED and LEDI/NTC) turn

off. When the thermal shutdown threshold is tripped a '1' gets

written to bit [1] of the Flag Register (Thermal Shutdown bit).

The LM3561 will start up again when the die temperature falls

to below +135°C, the Flags Register is read back, and the

device is re-enabled.

TX1 AND TX2 INTERRUPT FLAGS

The TX1 and TX2 interrupt flags (bits [3] and [4] of the Flags

read back a '1' if TX1/TORCH is in TX1 mode and the pin has

changed from low to high since the last read of the Flags

the pin has had a TX event since the last read of the Flags

these bits.

LED FAULT

The LED Fault flag (bit 2 of the Flags Register) reads back a

'1' if the part is active in Flash or Torch mode and the current

source (LED) experiences an open or short condition. An LED

open condition is signaled if the OVP threshold is crossed at

OUT. An LED short condition is signaled if the voltage at LED

goes below 500mV.

A TX event can be either a high to low transition or a low to

high transition depending on the setting of the TX1 or TX2

polarity bits (see Table 10).

There is a delay of 250µs before the LEDF flag is valid on a

LED short. This is the time from when V_LEDfalls below the

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I²C-Compatible Interface

START AND STOP CONDITIONS

The LM3561 is controlled via an I²C-compatible interface.

START and STOP conditions classify the beginning and end

of the I²C session. A START condition is defined as SDA

transitioning from HIGH to LOW while SCL is HIGH. A STOP

condition is defined as SDA transitioning from LOW to HIGH

while SCL is HIGH. The I²C master always generates the

START and STOP conditions.

30113918

FIGURE 12. Start and Stop Sequences

The I²C bus is considered busy after a START condition and

free after a STOP condition. During data transmission the

I²C master can generate repeated START conditions. A

START and a repeated START condition are equivalent func-

tion-wise. The data on SDA must be stable during the HIGH

period of the clock signal (SCL). In other words, the state of

SDA can only be changed when SCL is LOW. Figure 1 and

Figure 13 show the SDA and SCL signal timing for the I²C-

compatible Bus. See the Electrical Characteristics Table for

timing values.

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301139119

FIGURE 13. I²C-Compatible Timing

I²C-COMPATIBLE CHIP ADDRESS

The 7 bit I²C-compatible device address for the LM3561 is

1010011 (53). After the START condition, the I²C master

sends the 7-bit address followed by an eighth bit, read or write

(R/W). R/W = 0 indicates a WRITE (0xA6) and R/W = '1' in-

dicates a READ (0xA7). The second byte following the device

address selects the register address to which the data will be

written. The third byte contains the data for the selected reg-

ister.

30113920

FIGURE 14. Device Address

TRANSFERRING DATA

Every byte on the SDA line must be eight bits long with the

most significant bit (MSB) transferred first. Each byte of data

must be followed by an acknowledge bit (ACK). The acknowl-

edge related clock pulse (9th clock pulse) is generated by the

master. The master releases SDA (HIGH) during the 9th clock

pulse (write mode). The LM3561 pulls down SDA during the

9th clock pulse, signifying an acknowledge. An acknowledge

is generated after each byte has been received.

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TABLE 1. LM3561 Internal Registers

Enable Register

Internal Hex Address

Power On or Reset Value

0x10

0x12

0x20

0x80

0xA0

0xB0

0xC0

0xD0

0xE0

0xF0

0xF8

0x80

0xF8

0xFA

0xFD

0xEF

0x00

0x6A

0xF0

Indicator Brightness Register

GPIO Register

VIN Monitor Register

Torch Brightness Register

Flash Brightness Register

Flash Duration Register

Flags Register

Configuration Register 1

Configuration Register 2

ENABLE REGISTER (ADDRESS 0x10)

The Enable Register contains the enable bits that turn on the device in Indicate Mode, Torch Mode, or Flash Mode (bits[1:0]).

These bits are always reset at the end of a flash pulse. Bit [2] sets the STROBE level or edge control.

TABLE 2. Enable Register Bit Settings

Bits[7:3]

Not Used

Bit 2

Bits [1:0]

Enable Bits

(Strobe Level or Edge, STR bit)

N/A

0 = STROBE Input set for Level. Flash current Enable Bits

turns on when STROBE input is high and turns 00 = Shutdown (default)

off when STROBE either goes low or the 01 = Indicator Mode

Timeout Duration expires (default)

10 = Torch Mode

1 = STROBE Input set for edge triggered. Flash 11 = Flash Mode (bits reset at timeout)

current turns on when STROBE sees a rising

edge. Flash pulse turns off when timeout

duration expires

INDICATOR BRIGHTNESS REGISTER (ADDRESS 0x12)

The Indicator Register contains the bits to set the indicator current level in indicate mode.

TABLE 3. Indicator Brightness Register Bit Settings

Bits [7:3]

Bits [2:0]

Not Used

Indicate Current Settings

N/A

000 = 2.25mA (default)

001 = 4.5mA

010 = 6.75mA

011 = 9mA

100 = 11.25mA

101 = 13.5mA

110 = 15.75mA

111 = 18mA

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GPIO REGISTER (ADDRESS 0x20)

The GPIO register contains the control bits which change the state of the TX1/TORCH/GPIO1 pin and the TX2/GPIO2 pin to general

purpose I/O’s (GPIO’s).

TABLE 4. GPIO Register Bit Settings

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Not Used

TX2/GPIO2/

INT Interrupt data

Output

TX2/GPIO2

data direction Control

TX2/GPIO2

TX1/GPIO1

data

TX1/GPIO1

data direction Control

TX1/GPIO1

N/A

0 = INT mode This bit is the 0 = TX2/

0 = TX2/

GPIO2 is a

This bit is the 0 = TX1/

read or write GPIO1 is a

0 = TX1/

GPIO1 is

is disabled

read or write

GPIO2 is a

(default)

1 = When TX2/ GPIO2 in

GPIO2 is GPIO mode

data for TX2/ GPIO Input

flash interrupt data for TX1/ GPIO input

configured as

flash interrupt

input(default)

1 = TX1/

(default)

1 = TX2/

input (default) GPIO1 in

(default)

1 = TX2/

GPIO2 is

GPIO mode

(default is 0) GPIO1 is a

1 = TX1/

configured as (default is 0) GPIO2 is a

a GPIO output

TX2/GPIO2/

INT is set for

INT mode and

will pull low

when either

the LED

GPIO Output configured as

a GPIO

GPIO output

GPIO1 is

configured as

a GPIO

Thermal Fault

Flag is set or

the VIN

Monitor Flag is

set

VIN MONITOR REGISTER (ADDRESS 0X80)

The VIN Monitor Register controls the on/off state of the VIN Monitor comparator as well as selects the 4 programmable thresholds.

TABLE 5. VIN Monitor Register Bit Settings

Bits [7:3]

Bits [2:1]

Bit 0

Not Used

VIN Monitor Threshold Settings

VIN Monitor Enable

N/A

00 = 2.9V threshold (V_INfalling)

Default

0 = VIN Monitor Comparator is

disabled (default)

1 = VIN Monitor Comparator is

enabled.

01=3.0V threshold (V_INfalling)

10 = 3.1V threshold (V_INfalling)

11 = 3.2V threshold (V_INfalling)

TORCH BRIGHTNESS REGISTER (0XA0)

The Torch Brightness Register contains the bits to program the LED current in Torch Mode.

TABLE 6. Torch Brightness Register Bit Settings

Bits [7:3]

Bits [2:0]

Not Used

Torch Current Settings

N/A

000 = 18mA

001 = 36.8mA

010 = 55.6mA (default)

011 = 74.4mA

100 = 93.2mA

101 = 112mA

110 = 130.8mA

111 = 149.6mA

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FLASH BRIGHTNESS REGISTER (ADDRESS 0XB0)

The Flash Brightness Register contains the bits to program the LED current in flash mode.

TABLE 7. Flash Brightness Register Bit Settings

Bits [7:4]

Bits [3:0]

Not Used

Flash Current Settings

N/A

0000 = 36mA

0001 = 73.6mA

0010 = 111.2mA

0011 = 148.8mA

0100 = 186.4mA

0101 = 224mA

0110 = 261.6mA

0111 = 299.2mA

1000 = 336.8mA

1001 = 374.4mA

1010 = 412mA

1011 = 449.6mA

1100 = 487.2mA

1101 = 524.8mA Default

1110 = 562.4mA

1111 = 600mA

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FLASH DURATION REGISTER (ADDRESS 0XC0)

Bits [4:0] of the Flash Duration Register set the Flash timeout duration. Bit [5] sets the switch current limit.

TABLE 8. Flash Timeout Duration Register Bit Settings

Bit [7:6]

Not Used

Bit 5

Current Limit

Select

Bits [4:0]

Flash Timeout Duration Settings

N/A

0 = 1A Peak 00000 = 32ms timeout

Current Limit 00001 = 64ms timeout

1 = 1.5A Peak 00010 = 96ms timeout

Current Limit 00011 = 128ms timeout

(default)

00100 = 160ms timeout

00101 = 192ms timeout

00110 = 224ms timeout

00111 = 256ms timeout

01000 = 288ms timeout

01001 = 320ms timeout

01010 = 352ms timeout

01011 = 384ms timeout

01100 = 416ms timeout

01101 = 448ms timeout

01110 = 480ms timeout

01111 = 512ms timeout (default)

10000 = 544ms timeout

10001 = 576ms timeout

10010 = 608ms timeout

10011 = 640ms timeout

10100 = 672ms timeout

10101 = 704ms timeout

10110 = 736ms timeout

10111 = 768ms timeout

11000 = 800ms timeout

11001 = 832ms timeout

11010 = 864ms timeout

11011 = 896ms timeout

11100 = 928ms timeout

11101 = 960ms timeout

11110 = 992ms timeout

11111 = 1024ms timeout

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FLAGS REGISTER (ADDRESS 0XD0)

The Flags Register holds the status of the flag bits indicating LED Failure, Over-Temperature, the Flash Timeout expiring, VIN

Monitor Fault, LED over temperature (NTC), and a TX1 or TX2 interrupt.

TABLE 9. Flags Register Bit Settings

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

VIN Monitor

Flag

Not Used

LED Thermal TX2 Interrupt TX1 Interrupt Led Fault

Thermal

Shutdown

(TSD)

Flash Timeout

(TO)

Fault

(LEDF)

(NTC)

0 = No Fault at N/A

VIN (default)

1 = Input

Voltage

Monitor is

0 =LEDI/NTC 0=TX2 has not 0=TX1/

0 = Proper

0 = Die

0 = Flash

pin is above

V_TRIP(default) (default)

changed state TORCH has

not changed

state (default) 1 = LED Failed Shutdown

LED Operation Temperature timeout did not

(default) below Thermal expire

1=TX2 has

changed state 1=TX1/

(default)

1=LEDI/NTC

has fallen

below V_TRIP

(NTC mode

only)

(Open or

Short)

Limit (default) 1 = Flash

1 = Die

Temperature Expired

has crossed

the Thermal

Shutdown

enabled and

VIN has fallen

(TX2 mode

only)

TORCH pin

has changed

state (TX1

timeout

below (V_{IN_TH}

)

mode only)

Threshold of

+150°C

CONFIGURATION REGISTER 1 (ADDRESS 0XE0)

Configuration Register 1 contains the STROBE enable/disable bit, the STROBE polarity bit, the NTC enable bit, the polarity se-

lection for TX1 and TX2 flash interrupts, and the hardware torch mode enable for TX1/TORCH.

TABLE 10. Configuration Register 1 Bit Settings

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Hardware

Torch Mode

Enable

TX2 Polarity

TX1 Polarity

NTC Mode

Enable

STROBE

Polarity

STROBE Input Not Used

Enable

Not Used

0 = TX1/

TORCH is a

TX1 flash

0 = TX2 is set 0 = TX1 is set 0 = LEDI/NTC 0 = STROBE 0 = STROBE N/A

for active low for active low is a Indicator set for active Input Disabled

N/A

polarity

Current

low polarity

(default)

interrupt input 1 = TX2 is set 1 = TX1 is set Source Output 1 = STROBE 1 = STROBE

(default)

for active high for active high (default)

set for active Input Enabled

1 = TX1/

polarity

1 = LEDI/NTC high polarity

TORCH pin is (default)

a hardware

TORCH

enable. This

bit is reset to 0

after a flash

event.

(default)

is a

(default)

Comparator

Input for LED

Temperature

Sensing

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CONFIGURATION REGISTER 2 (ADDRESS 0XF0)

Configuration Register 2 contains the TX2 shutdown bit, the NTC shutdown bit, the Alternate External Torch Enable bit, and the

VIN Monitor Shutdown bit.

TABLE 11. Configuration Register 2 Bit Settings

Bit 3

V_INMonitor

Shutdown

Bit 1

NTC

Shutdown

Bits [7:4]

Not Used

Bit 2

AET mode

Bit 0

TX2 Shutdown

N/A

0 = If IN drops 0 = Normal

0 = LEDI/NTC 0 = TX2

below V_{IN_TH}operation for pin going

interrupt event

forces the

TX1/TORCH below V_TRIP

and the VIN

Monitor

feature is

enabled, the

LEDs are

forced into

Torch mode

(default)

1 = If IN drops

below V_{IN_TH}

and the VIN

Monitor

high before

STROBE (TX1

mode only)

default

1 = Alternate

External Torch

Mode. TX1/

TORCH high

before

flash LED into

Torch mode

(TX2 mode

only) default

1 = TX2

interrupt event

forces the

flash LED into

shutdown

forces the

LEDs into

Torch mode

(NTC mode

only) default

1 = LEDI/NTC

pin going

below V_TRIP

forces the

LEDs into

shutdown

(NTC mode

only)

STROBE

(TX2 mode

only)

forces Torch

mode with no

timeout (TX1

mode only)

feature is

enabled, the

LEDs turn off

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The output voltage ripple due to the output capacitors ESR is

found by:

Applications Information

OUTPUT CAPACITOR SELECTION

The LM3561 is designed to operate with a at least a 10µF

ceramic output capacitor. When the boost converter is run-

ning the output capacitor supplies the load current during the

boost converters on-time. When the NMOS switch turns off

the inductor energy is discharged through the internal PMOS

switch supplying power to the load and restoring charge to the

output capacitor. This causes a sag in the output voltage dur-

ing the on-time and a rise in the output voltage during the off-

time. The output capacitor is therefore chosen to limit the

output ripple to an acceptable level depending on load current

and input/output voltage differentials and also to ensure the

converter remains stable.

In ceramic capacitors the ESR is very low so assume that 80%

of the output voltage ripple is due to capacitor discharge and

20% from ESR. Table 12 lists different manufacturers for var-

ious output capacitors and their case sizes suitable for use

with the LM3561.

For proper LED operation the output capacitor must be at

least a 10µF ceramic. Larger capacitors such as 22µF can be

used if lower output voltage ripple is desired. To estimate the

output voltage ripple considering the ripple due to capacitor

discharge (ΔV_Q) and the ripple due to the capacitors ESR

(ΔV_ESR) use the following equations:

INPUT CAPACITOR SELECTION

Choosing the correct size and type of input capacitor helps

minimize the voltage ripple caused by the switching of the

LM3561’s boost converter and reduces noise on the devices

input terminal that can feed through and disrupt internal ana-

log signals. In the Typical Application Circuit a 10µF ceramic

input capacitor works well. It is important to place the input

capacitor as close as possible to the LM3561’s input (IN) ter-

minals. This reduces the series resistance and inductance

that can inject noise into the device due to the input switching

currents. Table 12 lists various input capacitors recommend-

ed for use with the LM3561.

For continuous conduction mode, the output voltage ripple

due to the capacitor discharge is:

TABLE 12. Recommended Input/Output Capacitors (X5R Dielectric)

Manufacturer

TDK Corporation

Murata

Part Number

C1608JB0J106M

Value

10µF

22µF

10µF

22µF

Case Size

Voltage Rating

0603(1.6mm×0.8mm×0.8mm)

0805(2mm×1.25mm×1.25mm)

6.3V

10V

6.3V

10V

6.3V

C2012JB1A106M

C2012JB0J226M

GRM21BR61A106KE19

GRM21BR60J226ME39L

Murata

INDUCTOR SELECTION

mance ensure that the inductor saturation and the peak cur-

rent limit setting of the LM3561 is greater than I_PEAK. This can

be calculated by:

The LM3561 is designed to use a 1µH to 2.2µH inductor.

Table 13 lists various inductors that can work well with the

LM3561. When the device is boosting (V_OUT> V_IN) the induc-

tor will typically be the biggest area of efficiency loss in the

circuit. Therefore, choosing an inductor with the lowest pos-

sible series resistance is important. Additionally, the satura-

tion rating of the inductor should be greater than the maximum

operating peak current of the LM3561. This prevents excess

efficiency loss that can occur with inductors that operate in

saturation. For proper inductor operation and circuit perfor-

ƒ_SW= 2MHz, and η can be found in the Typical Performance

Characteristics plots.

TABLE 13. Recommended Inductors

Manufacturer

Coilcraft

TDK

Part Number Dimensions (L×W×H)

R_DC

81mΩ

73mΩ

90mΩ

71mΩ

100mΩ

70mΩ

I_SAT

1.6A

2.7A

1.65A

1.5A

1.9A

1µH

XPL2010-102ML

VLS252012T-1R0N

VLS2010-1R0N

2mm×1.9mm×1mm

2mm×2.5mm×1.2mm

2mm x 2mm x 1mm

TDK

VLS2012ET-1R0N

VLS20160ET-1R0N

VLS252010ET-1R0N

2mm x 2mm x 1.2mm

2mm x 1.6mm x 0.95mm

2.5mm x 2mm x 1mm

TDK

NTC THERMISTOR SELECTION

a comparator input for flash LED thermal sensing. The ther-

mal sensing circuit consists of a negative temperature coef-

Programming bit [4] of Configuration Register 1 with a (1) se-

lects Thermal Comparator mode, making the LEDI/NTC pin

www.national.com

ficient (NTC) thermistor and a series resistor which forms a

resistive divider (see Figure 15).

30113966

FIGURE 15. NTC Circuit

The NTC thermistor senses the LEDs temperature via con-

ducting the LEDs heat into the NTC thermistor. Heat conduc-

tion is improved with a galvanic connection at GND (LED

cathode and NTC thermistor GND terminal) and by placing

the thermistor in very close proximity to the flash LED.

where R(T)_TRIPis the thermistor's value at the temperature

trip point, V_BIASis the bias voltage for the thermistor circuit,

and V_TRIP= 1V (typical). Choosing R_BIAShere gives a more

linear response around the temperature trip voltage. For ex-

ample with V_BIAS= 1.8V and a thermistor whose nominal

value at +25°C is 10kΩ and a β = 3380K, the trip point is cho-

sen to be +93°C. The value of R(T) at 93°C is:

NTC thermistors have a temperature to resistance relation-

ship of:

where β is given in the thermistor datasheet and R_25Cis the

thermistor's value at +25°C. R_BIASis chosen so that it is equal

to:

Figure 16 shows the linearity of the thermistor resistive divider

of the previous example.

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VLEDI/NTC vs Temp (V_BIAS= 1.8V, THERMISTOR = 10kΩ @+25C, β = 3380, R_BIAS=972Ω)

30113934

FIGURE 16. Thermistor Resistive Divider Response vs Temperature

Another useful equation for the thermistor resistive divider is

for practical values of thermistors, series resistors (R3), or

reference voltages V_BIAS

developed by combining the equations for R_BIAS, and R(T)

and solving for temperature. This gives the following relation-

ship.

NTC THERMISTOR PLACEMENT

The termination of the thermistor must be done directly to the

cathode of the Flash LED in order to adequately couple the

heat from the LED into the thermistor. Consequentially, the

noisy environment generated from the switching of the

LM3561's boost converter can introduce noise from GND into

the thermistor sensing input. To filter out this noise it is nec-

essary to place a 0.1µF or larger ceramic capacitor close to

the LEDI/NTC pin. The filter capacitor's return must also con-

nect with a low-impedance trace, as close as possible to the

GND pin of the LM3561.

Using a spreadsheet such as Excel, different curves for the

temperature trip point T(°C) can be created vs R_BIAS, Beta, or

V_BIASin order to help better choose the thermal components

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4. Avoid routing logic traces near the SW node so as to

avoid any capacitively coupled voltages from SW onto

any high impedance logic lines such as TX1/TORCH/

GPIO1, TX2/GPIO2/INT, HWEN, LEDI/NTC (NTC

mode), SDA, and SCL. A good approach is to insert an

inner layer GND plane underneath the SW node and

between any nearby routed traces. This creates a shield

from the electric field generated at SW.

Layout Recommendations

The high frequency and relatively large switching currents of

the LM3561 make the choice of layout important. The follow-

ing steps should be used as a reference to ensure the device

is stable and maintains proper voltage and current regulation

across its intended operating voltage and current range.

1. Place C_INon the top layer (same layer as the LM3561)

and as close to the device as possible. The input

capacitor conducts the driver currents during the low-

side MOSFET turn-on and turn-off and can see current

spikes over 500mA in amplitude. Connecting the input

capacitor through short wide traces on both the IN and

GND terminals will reduce the inductive voltage spikes

that occur during switching and which can corrupt the

V_INline.

5. Terminate the Flash LED cathode directly to the GND pin

of the LM3561. If possible, route the LED return with a

dedicated path so as to keep the high amplitude LED

current out of the GND plane. For a Flash LED that is

routed relatively far away from the LM3561, a good

approach is to sandwich the forward and return current

paths over the top of each other on two adjacent layers.

This will help in reducing the inductance of the LED

current paths.

2. Place C_OUTon the top layer (same layer as the LM3561)

and as close as possible to the OUT and GND terminal.

The returns for both C_INand C_OUTshould come together

at one point, and as close to the GND pin as possible.

Connecting C_OUTthrough short wide traces will reduce

the series inductance on the OUT and GND terminals

that can corrupt the V_OUTand GND line and cause

excessive noise in the device and surrounding circuitry.

6. The NTC Thermistor is intended to have its return path

connected to the LED's cathode. This allows the

thermistor resistive divider voltage (V_NTC) to trip the

comparators threshold as V_NTCis falling. Additionally, the

thermistor to LED cathode junction can have low thermal

resistivity since both the LED and the thermistor are

electrically connected at GND. The draw back is that the

thermistor's return will see the switching currents from

the LM3561's boost converter. Because of this, it is

necessary to have a filter capacitor at the NTC pin which

terminates close to the GND of the LM3561 and which

can conduct the switched currents to GND.

3. Connect the inductor on the top layer close to the SW pin.

There should be a low-impedance connection from the

inductor to SW due to the large DC inductor current, and

at the same time the area occupied by the SW node

should be small so as to reduce the capacitive coupling

of the fast dV/dt present at SW that can couple into

nearby traces.

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Physical Dimensions inches (millimeters) unless otherwise noted

12 Bump micro SMD (0.4mm pitch)

For Ordering, Refer to Ordering Information Table

NS Package Number TMD12AAA

X1 = 1.215mm (±0.03mm), X2 = 1.615mm (±0.03mm), X3 = 0.6mm(±0.075mm)

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LM3561 [TI]

相关型号：

LM3561TME

LM3561TME/NOPB

LM3561TMX

LM3561TMX/NOPB

LM3565

LM3565TLE/NOPB

LM3565TLX-0A/NOPB

LM3565TLX-0B/NOPB

LM3565TLX/NOPB

LM3570

LM3570SD

LM3570SD/NOPB