MAX5008CUB 查看數據表（PDF） - Maxim Integrated

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MAX5008CUB

Regulated 5V USB Charge Pump with Programmable Current Limit

Maxim Integrated 

Regulated 5V USB Charge Pump with

Programmable Current Limit

Pin Description

PIN

NAME

FUNCTION

1

RCS

External Current-Sense Resistor. Connect a resistor from RCS to OUT to set the overcurrent

threshold. ILIMIT = 60mV / RCS.

2

OUT

Fixed 5V Output. Bypass OUT to GND with a 4.7µF capacitor.

3

FAULT

Output Fault Indicator. FAULT is asserted when either IOUT > ILIMIT or VOUT < VTH. FAULT is an

open-drain output that is high during normal operation or during shutdown.

4

GND

Ground Pin. Connect GND to PGND.

5

SHDN

Shutdown Input. When SHDN = low, the device turns off. Drive SHDN high or connect to IN for

normal operation.

6

PGND

Power Ground Pin. Connect PGND to GND.

7

CXN

Negative Terminal of the Charge-Pump Capacitor. Connect a 0.68µF capacitor from CXN to CXP.

8

IN

Input Supply, 2.95V to 5.5V. Bypass IN to GND with a 4.7µF ceramic capacitor.

9

CXP

Positive Terminal of the Charge-Pump Capacitor. Connect a 0.68µF capacitor from CXP to CXN.

10

CEXT

Charge-Pump Output. Bypass CEXT to PGND with a 6.8µF capacitor.

Detailed Description

The MAX5008 charge pump provides a regulated 5V

output from a 2.95V to 5.5V input. The device delivers a

maximum of 125mA load current. Designed specifically

for compact applications, a complete regulator circuit

requires a minimum number of external components.

Adjustable Current Limit

The MAX5008 has an adjustable overcurrent protec-

tion. An external current-sense resistor is connected

from RCS to OUT to set the current limit. The current

limit is defined by:

ILIMIT = VCS / RCS

where VCS is the current-sense trip level, typically 60mV.

For example, ILIMIT = 150mA when RCS = 0.40Ω.

When the output current limit is exceeded, the output

voltage falls and the device maintains the average out-

put current at ILIMIT. Upon removal of the overcurrent

condition, the part resumes normal operation.

FAULT Indication

When IOUT > ILIMIT or VOUT < VTH, FAULT asserts.

FAULT is an open-drain output that needs to be con-

nected through a 100kΩ (typ) pullup resistor to a logic

supply voltage.

Thermal Shutdown

The MAX5008 has internal thermal shutdown circuitry,

which shuts down the device when the die temperature

exceeds +150°C. The thermal shutdown circuitry has

30°C hysteresis.

Shutdown Mode

Driving SHDN low places the device in shutdown

mode, which disables the oscillator, the control logic,

and the reference. The output goes into high-imped-

ance state and drops to ground if loaded. Placing the

device in shutdown mode reduces the supply current

to less than 0.1µA. In normal operation, SHDN is driven

high or connected to IN.

Applications Information

Capacitor Selection

The MAX5008 requires four external capacitors. Their

values depend on the required output current. Table 1

shows the capacitor values recommended for different

load currents.

Input Voltage Range

The MAX5008 maintains a regulated 5V output with

input voltages from 2.95V to 5.5V. If the input voltage

exceeds 4.25V, limit the output current to 75mA or less.

This keeps the MAX5008 within its maximum power dis-

sipation limits.

Table 1. Recommended Capacitor Values

IOUT

50mA

125mA

CIN (µF)

3.3

4.7

CX (µF)

0.33

0.68

CEXT (µF)

3.3

6.8

COUT (µF)

3.3

4.7

Layout Considerations

All capacitors should be located as close to the IC as

practical. Connect GND and PGND through a short,

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