MAX886ECJ 查看數據表（PDF） - Maxim Integrated

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MAX886ECJ

Wireless and Satellite Handset Power-Management ICs

Maxim Integrated 

Wireless and Satellite Handset

Power-Management ICs

For example:

VREF = 1.25V

VTHF = falling threshold = 2.52V

VHYS = hysteresis = 0.1V

VTHR = rising threshold = VTHF + VHYS = 2.62V

R1 = 619kΩ (1%)

R2 = 562kΩ (1%)

R3 = 47.6kΩ (1%)

Power-On Sequence

(Including RESET and Startup Timers)

Drive ON low to begin the power-up sequence. To reduce

overall system cost and complexity, the MAX886/MAX888/

MAX1863 incorporate RESET and startup timers with the

power-on sequence.

The MAX886/MAX888/MAX1863 turn on the reference

when ON goes low. Once the reference is fully pow-

ered up, if the input voltage exceeds the internal under-

voltage-lockout threshold (UVLOR), Regulator 0 turns

on. Once OUT0 is in regulation, OUT2 and OUT4 turn

on. Once OUT2 is in regulation, OUT1 and OUT5 turn

on and the 75ms reset timer begins. RESET remains

low from the time OUT2 is valid until the reset timer

times out. After the reset period expires, a 50ms startup

timer begins. The MAX886/MAX888/MAX1863 shut

down if the external logic or controller fails to drive OFF

high before the startup timer expires. Drive OFF high to

continue operation. Driving OFF low turns off the IC.

There is no required sequence to power off any regula-

tor after the device has turned on. Regulators can be

powered off selectively by sending the correct code

through the serial interface (Table 1).

MAX886

MAX888

MAX1863 10k

OUT2

RESET

ON

ONSTAT

µC

OFF

Figure 4. One-Button On/Off Control with ONSTAT

ONSTAT Output

ONSTAT is a logic output that follows ON. Connect

ONSTAT to the external logic or controller to sense

when the ON pin has been brought low to request shut-

down. This allows easy implementation of a one-button

on/off control scheme (Figure 4).

Thermal Overload Protection

An internal thermal sensor shuts the MAX886/MAX888/

MAX1863 down when the maximum temperature limit is

exceeded (160°C typical).

I2C-Compatible Serial Interface

Use an I2C-compatible serial interface to turn the

MAX886/MAX888/MAX1863 on and off, as well as con-

trol each regulator’s output voltage and program the

DC-DC converter and charge pump’s oscillator frequen-

cy. Use standard I2C-compatible receive-byte com-

mands to program the IC. This part is always a slave to

the bus master. The chip address is 1001 111.

POR State

The power-on reset state of all the DAC and frequency

registers is 0Fh, except for DAC1 which is 04h. The

power-on reset state of the ONX bits is 1 (Table 1). The

power-on voltage for each regulator is shown in bold in

Tables 2, 3, and 5.

Applications Information

Inductor Selection

The essential parameters for inductor selection are

inductance and current rating. The MAX886/MAX888/

MAX1863 operate with a wide range of inductance val-

ues. In many applications, values between 10µH and

68µH take best advantage of the controller’s high switch-

ing frequency.

Calculate the minimum inductance value using the sim-

plified equation:

( ) L(MIN) =

4VBATT(MAX) −

VOUT0





IPEAK × fOSC × VBATT / VOUT0

where IPEAK is the peak inductor current (0.9A) and

fOSC is the switching frequency.

For example, for a 6V battery voltage, a desired VOUT0

is 3.3V, the oscillator frequency is 375kHz, and 15µH is

the minimum inductance required.

Diode Selection

The MAX886/MAX888/MAX1863s’ high switching fre-

quency demands a high-speed rectifier. Schottky

diodes, such as the 1N5817–1N5822 family or surface-

mount MBR0520L series, are recommended. Ultra-

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