MAX8934D 查看數據表（PDF） - Maxim Integrated

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MAX8934D

Dual-Input Linear Chargers, Smart Power Selector with Advanced Battery Temperature Monitoring

Maxim Integrated 

Dual-Input Linear Chargers, Smart Power Selector

with Advanced Battery Temperature Monitoring

MAX9834D), so input voltages greater than 5.3V (4.35V

for the MAX8934B/MAX8934C/MAX8934E) can increase

power dissipation in the limiter. The MAX8934_ input

limiter power loss is (VDC – VSYS) x IDC, where VSYS may

be as high as 5.3V for the MAX8934A or 4.35V for the

MAX8934B–MAX8934E. The input limiter power loss is

not less than 0.2I x IDC2. Also note that the MAX8934_

turns off when any input exceeds 6.9V (typ).

DC and USB Connections and

Current-Limit Options

Input Current Limit

The input and charger current limits are set as shown in

Tables 2a and 2b. It is often preferable to change the

input current limit as the input power source is changed.

The MAX8934_ facilitates this by allowing different input

current limits for DC and USB as shown in Tables 2a

and 2b.

When the input current limit is reached, the first action

taken by the MAX8934_ is to reduce the battery charge

current. This allows the regulator to stay in dropout, or

at 5.3V (MAX8934A), during heavy loads, thus reducing

power dissipation. If, after the charge current is reduced

to 0mA, the load at SYS still exceeds the input current

limit, SYS voltage begins to fall. When the SYS voltage

drops to BATT, the SYS-to-BATT switch turns on, using

battery power to support the system load during the load

peak. The MAX8934_ features flexible input connections

(at the DC and USB input pins) and current-limit settings

(set by PEN1, PEN2, PSET, and ISET) to accommodate

nearly any input power configuration. However, it is

expected that most systems use one of two external

power schemes: separate connections for USB and an

AC adapter, or a single connector that accepts either

USB or AC adapter output. Input and charger current

limit are controlled by PEN1, PEN2, RPSET, and RISET,

as shown in Tables 2a and 2b.

Separate Adapter and USB Connectors

When the AC adapter and USB have separate connec-

tors, the adapter output connects to DC and the USB

source connects to USB. PEN1 is permanently connected

high (to DC or VL). The DC current limit is set by RPSET,

while the USB current limit is set by PEN2 and USUS.

Single Common Connector

for USB or Adapter

When a single common connector is used for both AC

adapter and USB sources, the DC input is used for

both input sources. The unused USB inputs should be

grounded when an AC adapter is connected at DC,

PEN1 should be pulled high to select the current limit

set by RPSET. When a USB source is connected, PEN1

should be low to select 500mA, 100mA, or USB suspend

(further selected by PEN2 and USUS). PEN1 can be

pulled up by the AC adapter power to implement hard-

ware adapter/USB selection.

USB Suspend

Driving USUS high when PEN1 is low turns off charging,

as well as the SYS output and reduces input current to

190FA to accommodate USB suspend mode.

Power Monitor Outputs (UOK, DOK)

DOK is an open-drain output that pulls low when the DC

input has valid power. UOK is an open-drain output that

pulls low when the USB input has valid power. A valid

input for DC or USB is between 4.1V and 6.6V. If a single

power-OK output is preferred, DOK and UOK can be

Table 2a. Input Limiter Control Logic (MAX8934A/MAX8934B/MAX8934C/MAX8934E)

POWER

SOURCE

DOK

UOK

PEN1

PEN2

USUS

DC INPUT

USB INPUT MAXIMUM CHARGE

CURRENT LIMIT CURRENT LIMIT

CURRENT*

AC adapter at

DC input

L

X

L

X

USB power at

DC input

L

X

L

X

USB power at

H

L

USB input; DC H

L

unconnected

H

L

H

X

L

H

L

L

L

X

X

H

X

L

X

X

X

3000V/RPSET

USB input off;

L

475mA

DC input has

L

95mA

priority

H

USB suspend

L

475mA

L

95mA

H

No DC input

USB suspend

3000V/RISET

475mA

95mA

0

3000V/RISET

0

DC and USB

unconnected

H

H

X

X

X

No USB input

0

*Charge current cannot exceed the input current limit. Charge may be less than the maximum charge current if the total SYS load

exceeds the input current limit.

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