LM3280TLSLASHNOPB datasheet(5/27 Pages) TI

5 / 27 page

LM3280

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SNOSAU4B – OCTOBER 2006 – REVISED FEBRUARY 2013

Buck Electrical Characteristics

(1)(2)(3) (continued)

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

range (

−30°C ≤ TA = TJ ≤ +85°C). Unless otherwise noted, specifications apply to the LM3280 with: VIN = ( SVIN = PVIN = )

3.6V, ENBUCK = 3.6V, ENLDO1 = ENLDO2 = ENLDO3 = BYP = 0V, FB = 2V, VCON = 0.267V.

Symbol

Parameter

Conditions

Min.

Typ.

Max

Units

ILIM-PWM

Switch Current Limit

FB = 0V (6)

700

820

940

ILIM-BYP

Bypass FET Current Limit

(7)

800

1000

1200

FOSC

Internal Oscillator Frequency

1.8

2.2

MHz

Gain

VCON to VOUT Gain

0.267V

≤ VCON ≤ 1.20V,

V/V

VIN = 4.2V

ICON

VCON Input Leakage Current

VCON = 1.2V

(6)

Electrical Characteristic table reflects open loop data (FB = 0V and current drawn from SW pin ramped up until cycle by cycle current

limit is activated). Refer to datasheet curves for closed loop data and its variation with regards to supply voltage and temperature.

Closed loop current limit is the peak inductor current measured in the application circuit by increasing output current until output voltage

drops by 10%.

(7)

The current is defined as the load current at which the BYPOUT voltage is 1V lower than PVIN.

Buck System Characteristics

(1) (2)

The following spec table entries are guaranteed by design if the component values in the typical application circuit are used.

These parameters are not guaranteed by production testing.

Symbol

Parameter

Conditions

Min

Typ

Max

Units

TRESPONSE

Time for VOUT to Rise from

VIN = 4.2V, COUT = 4.7µF,

0.8V to 3.4V in PWM Mode

RLOAD = 15Ω

µs

L = 2.2 µH (ISAT > 0.94A)

TSTARTUP

Time for VOUT to rise to 3.4V

VIN = 4.2V, COUT = 4.7µF,

in PWM Mode

RLOAD = 15Ω

µs

(3)

L = 2.2µH (ISAT = 0.94A)

EN = Low to High

CCON

VCON Input Capacitance

VIN = 3.6V, VCON = 1V,

Test Freq. = 100kHz

TON_BYP

Bypass FET Turn On Time In

VIN = 3.6V, VCON = 0.267V,

Bypass Mode

COUT = 4.7µF, RLOAD = 15Ω

µs

BYP = Low to High

TBYP

Auto Bypass Detect Delay

(4)

µs

Time

(1)

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

(2)

Shutdown current includes leakage current of PFET and Bypass FET.

(3)

The startup time is the time to reach 90% of 3.4V nominal output voltage from the ENBUCK being low to high.

(4)

SVIN is compared to the programmed output voltage (VOUT). When SVIN – VOUT falls below VBYPASS− for longer than TBYP the Bypass

FET turns on and the switching FETs turn off. This is called the Bypass mode. The device comes out of Bypass mode when SVIN –

VOUT exceeds VBYPASS

+ for longer than T

BYP, and PWM mode returns. The hysteresis for the bypass detection threshold VBYPASS

+ –

VBYPASS− will always be positive and will be approximately 200mV (typ.).

LDO1, 2, and 3 Electrical Characteristics

(1) (2)

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

range (

−30°C ≤ TA = TJ ≤ +85°C). Unless otherwise noted, specifications apply to the LM3280 with: VIN = 3.6V, ENBUCK =

3.6V, BYP = 0V, FB = 2V, VCON = 0.267V, ENLDOx = 3.6V

(3).

Symbol

Parameter

Conditions

Min

Typ

Max

Units

VLDO

LDO Output Voltage

VLDO = 2.85V, IOUT = 1mA

-1

Accuracy

-2

ΔVLDO

Line Regulation

VIN = VLDO(nom) + 0.5V to 5.5V,

0.1

%/V

IOUT = 1mA

Load Regulation

IOUT = 1mA to 20mA

0.01

0.04

%/mA

(1)

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

(2)

Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the

most likely norm.

(3)

The ENLDOx means that the one of ENLDO1, ENLDO2, and ENLDO3 is set high (> 1.2V) and the others are set 0V.

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