MP2637 datasheet(31/36 Pages) MPS

31 / 36 page

MP2637 –2.5A SINGLE CELL SW MODE BATTERY CHARGER WITH PPM AND 2.4A BOOST

MP2637 Rev. 1.04

www.MonolithicPower.com

8/3/2017

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

APPLICATION INFORMATION

COMPONENT SELECTION

Setting the Charge Current in Charge Mode

In charge mode, both the external sense resistor,

RS1, and the resistor RISET connect to the ISET

pin to set the charge current (ICHG) of the MP2637

(see the Typical Application circuit).

Given ICHG and RS1, RISET can be calculated as:

ISET

CHG

2400

(k )

(A) RS1(m )





(8)

For example, for ICHG

=2.5A, and RS1=20mΩ,

thus: RISET=

48kΩ.

Setting the Input Current Limiting in Charge

Mode

In charge mode, connect a resistor from the ILIM

pin to AGND to program the input current limit.

The relationship between the input current limit

and setting resistor is as following:

ILIM

IN _ LIM

(k )

(A)



(9)

where RILIM must exceed 16.5

kΩ, so that IIN_LIM is

in the range of 0A to 2.7A.

For

most

applications,

use

RILIM

= 50

kΩ

(IUSB_LIM=900mA) for USB3.0 mode, and use RILIM

= 90

kΩ (I

USB_LIM=500mA) for USB2.0 mode.

Setting the Input Voltage Range for Different

Operation Modes

A resistive voltage divider from the input to PWIN

pin determines the operating mode of MP2637.

PWIN

(V)

R4 R6





(10)

If the voltage on PWIN is between 0.8V and

1.15V, the MP2637 works in the charge mode.

While the voltage on the PWIN pin is not in the

range of 0.8V to 1.15V and VIN > 2V, the

MP2637 works in the boost mode (see Table 1)).

For a wide operating range, use a maximum

input voltage of 6V as the upper threshold for a

voltage ratio of:

PWIN

1.15

R4 R6





(11)

With the given R6, R4 is then:

PWIN





(12)

For a typical application, start with R6=5.1k

Ω, R4

is 21.5k

Ω.

Setting

the

Input

Voltage

Regulation

Charge Mode

In charge mode, connect a resistor divider from

the IN pin to AGND with tapped to REG pin to

program the input voltage regulation.

IN _ R

REG

R3 R5

(V)





(13)

With the given R5, R3 is:

IN _ R

REG

R5(V)





(14)

For a preset input voltage regulation value, say

4.75V, start with R5=5.1kΩ, R3 is 15kΩ.

NTC Function in Charge Mode

Figure 14 shows that an internal resistor divider

sets the low temperature threshold (VTL) and high

temperature threshold (VTH) at 66.6%·VSYS and

35%·VSYS,

respectively.

For

given

NTC

thermistor, select an appropriate RT1 and RT2 to

set the NTC window.







NTC_Cold

SYS

//R

(15)







NTC_Hot

SYS

//R

(16)

Where RNTC_Hot is the value of the NTC resistor at

the upper bound of its operating temperature

range, and RNTC_Cold is its lower bound.

The two resistors, RT1 and RT2, independently

determine the upper and lower temperature limits.

This flexibility allows the MP2637 to operate with

most NTC resistors for different temperature

range requirements. Calculate RT1 and RT2 as

follows:

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