FAN5601 Просмотр технического описания (PDF) - Fairchild Semiconductor

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FAN5601

Regulated Step-Down Charge Pump DC/DC Converter

Fairchild Semiconductor 

Shutdown, UVLO, Short Circuit Current Limit

and Thermal Shutdown

The device has an active-low shutdown pin to decrease supply

current to less than 1µA. In shutdown mode the supply is dis-

Switch Configuration

VIN

connected from the output. UVLO triggers when supply voltage

drops below 2V. When the output voltage is lower than 150mV, a

short circuit protection is triggered. In this mode 15 out of 16

pulses during the switching will be skipped and the supply cur-

rent is limited. Thermal shutdown triggers at 150°C.

VIN

S1

C+

S2

C

B

VOUT

S3

C-

S4

C

OUT

S1

C+

S2

VOUT

CB

S3

C-

S4

C

OUT

GND

Figure 2. (A)

2:1 configuration

Switches in charging phase

Reverse all switches for pumping phase

GND

Figure 2. (B)

1:1 configuration

Switch 3 is always off and

Switch 4 is always on

Switches 1 and 2 are in phase 1

Reverse the position of switches 1&2

for phase 2

Applications Information

Proper operation of the FAN5601 requires one ceramic bucket

capacitor in the 0.1µF to 1µF range; one 10µF output bypass

capacitor and one 10µF input bypass capacitor. In order to

obtain optimum output ripple and noise performance, use of low

ESR (<0.05Ω) ceramic input and output bypass capacitors is

recommended. The X5R and X7R rated capacitors provide ade-

quate performance over the -40°C to 85°C temperature range.

The value of the bucket capacitor is dependent on load current

requirements. A 1µF bucket capacitor will work well in all appli-

cations at all load currents, while a 0.1µF capacitor will support

most applications under 100mA of load current. The choice of

bucket capacitor values should be verified in the actual applica-

tion at the lowest input voltage and highest load current. A 30%

margin of safety is recommended in order to account for the tol-

erance of the bucket capacitor and the variations in the on-resis-

tance of the internal switches.

11

www.fairchildsemi.com

FAN5601 Rev. 1.0.5

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