LM3554 datasheet(5/47 Pages) TI1

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LM3554

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SNVS549C – JUNE 2009 – REVISED FEBRUARY 2016

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(1)

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

(2)

Minimum (MIN) and maximum (MAX) limits are ensured by design, test, or statistical analysis. Typical (TYP) numbers are not ensured,

but do represent the most likely norm. Unless otherwise specified, conditions for typical specifications are: VIN = 3.6 V and TA = 25°C.

(3)

The typical curve for overvoltage protection (OVP) is measured in closed loop using the Typical Application Circuit. The OVP value is

found by forcing an open circuit in the LED1 and LED2 path and recording the peak value of VOUT. The value given in Electrical

Characteristics 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.

At worst case is an open circuit condition where the output voltage can continue to rise after the OVP comparator trips by approximately

IIN× sqrt (L/COUT).

(4)

The typical curve for Current Limit is measured in closed loop using the Typical Application Circuit by increasing IOUT until the peak

inductor current stops increasing. The value given in Electrical Characteristics 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 20 ns × VIN / L.

6.5 Electrical Characteristics

Unless otherwise specified, typical limits are for TA = 25°C, minimum and maximum limits in apply over the full operating

ambient temperature range (–30°C

≤ TA ≤ +85°C), VIN = 3.6 V, and VHWEN = VIN.

(1) (2)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

CURRENT SOURCE SPECIFICATIONS

ILED

Current source

accuracy

600-mA flash LED setting,

VOUT = VIN

ILED1 and ILED2

1128

1200

1284

ILED1 or ILED2

541

600

657

17-mA torch current setting

VHR = 500 mV

ILED1 and ILED2

30.4

33.8

37.2

VHR

Current source

regulation voltage

(VOUT – VLED)

600-mA setting, VOUT = 3.75 V

300

IMATCH

LED Current

Matching

600-mA setting, VLED = 3.2 V

0.35%

STEP-UP DC-DC CONVERTER

VREG

Output voltage

accuracy

2.7 V

≤ VIN ≤ 4.2 V, IOUT = 0 mA

VENVM = VIN, OV bit = 0

4.8

5.2

VOVP

Output overvoltage

protection trip

point(3)

On threshold, 2.7 V

≤ VIN ≤ 5.5 V

5.4

5.6

5.7

Off threshold

5.3

RPMOS

PMOS switch on-

resistance

IPMOS = 1 A

150

Ω

RNMOS

NMOS switch on-

resistance

INMOS = 1 A

150

Ω

ICL

Switch current

limit(4)

CL bits = 00

0.711

1.05

1.373

CL bits = 01

1.295

1.51

1.8

CL bits = 10

1.783

1.99

2.263

CL bits = 11

2.243

2.45

2.828

IOUT_SC

Output short-circuit

current limit

VOUT < 2.3 V

550

ILED/NTC

Indicator current

LEDI/NTC bit = 0

IND1, IND0 bits = 00

2.3

IND1, IND0 bits = 01

4.6

IND1, IND0 bits = 10

6.9

IND1, IND0 bits = 11

8.2

VTRIP

Comparator trip

threshold

LEDI/NTC bit = 1, 2.7 V

≤ VIN ≤ 5.5 V

0.947

1.052

1.157

ƒSW

Switching frequency

2.7 V

≤ VIN ≤ 5.5 V

1.75

2.23

MHz

Quiescent supply

current

Device not switching

630

µA

ISHDN

Shutdown supply

current

2.7 V

≤ VIN ≤ 5.5 V

3.5

6.6

µA

tTX

Flash-to-torch LED

current settling time

TX_ Low to High, ILED1 + ILED2 = 1.2 A to 180 mA

µs

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