MAX1685EEE datasheet(4/14 Pages) MAXIM

4 / 14 page

Low-Noise, 14V Input, 1A, PWM

Step-Down Converters

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ELECTRICAL CHARACTERISTICS

(VIN = V SHDN = 6V, STBY = SYNC/PWM = CVL, VBOOT = VOUT, FB = AGND, circuit of Figure 1, TA = -40°C to +85°C, unless other-

wise noted.) (Note 5)

Note 1: The output adjust range with BOOT connected to VOUT is VREF to 5.5V. Connect BOOT to AGND for VOUT > 5.5V.

Note 2: The quiescent power-consumption specifications include chip supply and gate-drive loss only. Divide these values by VIN

(6V) to obtain quiescent currents. In normal and low-power modes, chip supply current dominates and quiescent power is

proportional to VBOOT (BOOT connected to OUT). In PWM mode, gate-drive loss dominates and quiescent power is propor-

tional to VIN ✕ (VIN - VCVH). In addition, IR losses in power switches and external components typically increase PWM quies-

cent power consumption by 5mW to 10mW. Note that if the device is not bootstrapped, additional power is dissipated in the

CVL linear regulator.

Note 3: When the duty factor (VOUT / VIN) is less than this value, the switching frequency decreases in PWM mode to maintain

regulation.

Note 4: Thermal shutdown is disabled in low-power mode (STBY = low) to reduce power consumption.

Note 5: Specifications to -40°C are guaranteed by design, not production tested.

CVL Undervoltage Lockout

Threshold

2.4

2.6

BOOT = AGND, CVL falling edge,

typical hysteresis is 40mV

Logic Input Low Voltage

VIL

0.7

Logic Input High Voltage

VIH

SHDN, STBY, SYNC/PWM

ILIM/SS Source Current

3.1

4.7

µA

VILIM/SS = 1.4V

0.27

Normal mode, SYNC/PWM = low,

VBOOT = 3.3V (Note 2)

BOOT Switchover Threshold

2.35

2.65

BOOT falling edge, typical hysteresis is 0.1V

CVH with Respect to VIN

-5.0

-4.1

ICVH = -1mA

CVL Regulator Output Voltage

2.7

3.15

VIN = 3V to 14V, BOOT = AGND,

ICVL = 0 to 5mA

Reference Output Voltage

1.232

1.268

IREF = 0

Oscillator Frequency

fOSC

480

700

kHz

MAX1685

240

350

MAX1684

Shutdown Supply Current

µA

SHDN = low

Quiescent Power Consumption

Current Limit in Low-Power

Mode

ILIMLP

285

475

STBY = low

Output Voltage (3.3V Mode)

VOUT

3.280

3.382

PARAMETER

SYMBOL

MIN

MAX

UNITS

FB Input Current

IFB

-50

Output Adjust Range

VREF

VIN

Output Current Capability

Input Voltage Range

2.7

Output Feedback Voltage

VFB

1.233

1.269

Current Limit in PWM Mode

ILIM

1.2

2.3

CONDITIONS

VFB = 1.4V

BOOT = AGND (Note 1)

VIN = 6V to 14V

FB = AGND, ILOAD = 0 to 1A

VFB = VOUT, ILOAD = 0 to 1A

Low-power mode, STBY = low,

VBOOT = 3.3V (Note 2)

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