LX2205 データシートの表示（PDF） - Microsemi Corporation

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LX2205

1A Li-Ion Battery Charger with Power Source Management

Microsemi Corporation 

LX2205

® 1A Li-Ion Battery Charger with Power Source Management

TM

PRODUCTION DATA SHEET

THEORY OF OPERATION / APPLICATION NOTE

MDC, USB OR-ING, UVLO AND DC OK

The power path from the USB input to the SYS pin

consists of a current limiter and a bidirectional switch

(capable of blocking current in either direction). The USB

input is switched off when at least one of the following

conditions exists:

1. VUSB < VUSBUVLO

2. USB Suspend pin is asserted.

3. VMDC > VUSB

4. VMDC > VDC OK _THRESHOLD

The MDC input is a monitoring input only, it is not a

high current input. When the voltage at SYS exceeds the

UVLO level, (typically 3.7V), the charger portion of the

circuit is activated. The DC OK output is pulled low when

both of the following conditions are true:

1. VMDC > VDC OK _THRESHOLD

2. VSYS > VBAT

Therefore when using a current limited wall adapter it is

possible to charge the battery and not assert the DC OK

output.

PROTECTION FEATURES

Conditioning Current Mode – If the battery terminal

voltage is less than 2.7V, the battery charger will reduce the

charge current to 5% of full scale. This also protects the

appliance from overheating by trying to drive the full

charging current into a short circuited battery.

Under Voltage Lockout – The charger remains inactive

until the under voltage lockout threshold is exceeded at the

SYS pin.

Thermal Control Loop – The power dissipation of the

charger is limited by reducing the charge current with a

control loop to prevent the die temperature from exceeded

approximately 140°C.

Reverse Current Blocking – Current will not flow out of

the USB pin.

Shutdown Mode – If the SHDN pin is logic high, the

charger enters a shutdown mode to prevent draining the

battery.

Battery Temperature Lockout – If an unsafe temperature is

sensed by the TFB input window comparator, battery

charging is suspended.

LAYOUT GUIDELINES

ƒ It is important when laying out the LX2205 to place

10µF ceramic capacitors as close to the SYS, USB and

VBAT IC terminals as possible to filter switching

transients.

ƒ It is important to provide a low thermal impedance path

from the thermal pad on the bottom of the LX2205

package to the ground plane of the circuit board to

maximize heat dissipation. Generally this is

accomplished by the use of multiple thermal vias.

ƒ The compensation capacitor should be placed close to

the CMP pin and connected with a short trace.

CHARGE CURRENT PROGRAMMING

The CCP, CTP, and CUS programming pins are used to

program the constant charge current, termination current,

and USB current, respectively. These pins utilize regulated

output voltages that produce a program current across an

external resistor to GND.

The following tables are guidelines for selecting the proper

resistor values:

Constant Charge Current (in mA)

RCCP

50

1270k

100

604k

200

294k

300

187k

400

137k

500

107k

600

88.7k

700

75.0k

800

63.4k

900

56.2k

1000

49.9k*

* RCCP minimum value

Termination Current (in mA)

5

RCTP

237k

10

105k

20

51.1k

40

24.9k

60

15.8k

80

11.8k

100

9.09k

120

7.50k

140

6.34k

160

5.49k

180

4.75k

200

4.22k

Copyright © 2007

Rev. 1.0a, 2007-03-02

Microsemi

Analog Mixed Signal Group

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

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