CDH2D09 datasheet(41/44 Pages) MAXIM

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THM threshold adjustment can be accommodated by

changing RTB, connecting a resistor in series and/or in

parallel with the thermistor, or using a thermistor with dif-

ferent material constant (

β). For example, a +45°C hot

threshold and 0°C cold threshold can be realized by

using a 10k

Ω thermistor with a β of 4250K and connect-

ing 120k

Ω in parallel. Since the thermistor resistance

near 0°C is much higher than it is near +50°C, a large

parallel resistance lowers the cold threshold, while only

slightly lowering the hot threshold. Conversely, a small

series resistance raises the cold threshold, while only

slightly raising the hot threshold. Raising RTB lowers

both the hot and cold thresholds, while lowering RTB

raises both thresholds.

PCB Layout and Routing

Good printed circuit board (PCB) layout is necessary to

achieve optimal performance. Refer to the MAX8671

evaluation kit for Maxim’s recommended layout.

Use the following guidelines for the best results:

• Use short and wide traces for high-current and dis-

continuous current paths.

• The step-down regulator power inputs are critical

discontinuous current paths that require careful

bypassing. Place the step-down regulator input

bypass capacitors as close as possible to each

switching regulator power input pair (PV_ to PG_).

• Minimize the area of the loops formed by the step-

down converters’ dynamic switching currents.

• The exposed paddle (EP) is the main path for heat

to exit the IC. Connect EP to the ground plane with

thermal vias to allow heat to dissipate from the

device.

• The MAX8671X regulator feedback nodes are sensi-

tive high-impedance nodes. Keep these nodes as

short as possible and away from the inductors.

• The thermistor node is high impedance and should

be routed with care.

• Make power ground connections to a power ground

plane. Make analog ground connections to an ana-

log ground plane. Connect the ground planes at a

single point.

• The REG4 LDO is a high-performance LDO with

high PSRR and low noise and care should be used

in the layout to obtain the high performance.

Generally, the REG4 LDO is powered from a step-

down regulator output, and therefore, its input

capacitor should be bypassed to the power ground

plane. However, its output capacitor should be

bypassed to the analog ground plane.

• BP is a high impedance node and leakage current

into or out of BP can affect the LDO output accuracy.

Package Marking

The top of the MAX8671X package is laser etched as

shown in Figure 15:

• “8671XETL” is the product identification code. The

full part number is MAX8671XETL; however, in this

case, the “MAX” prefix is omitted due to space

limitations.

• “yww” is a date code. “y” is the last number in the

Gregorian calendar year. “ww” is the week number

in the Gregorian calendar. For example:

“801” is the first week of 2008; the week of

January 1st, 2008

“052” is the fifty-second week of 2010; the

week of December 27th, 2010.

“aaaa” is an assembly code and lot code.

“+” denotes lead-free packaging and marks

the pin 1 location.

PMIC with Integrated Charger and

Smart Power Selector for Handheld Devices

______________________________________________________________________________________

TOP VIEW

THIN QFN

5mm x 5mm x 0.8mm

8671XE

TLyww

+ aaaa

Figure 15. Package Marking Example

Chip Information

PROCESS: BiCMOS

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