MAX17035(2009) 查看數據表（PDF） - Maxim Integrated

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MAX17035
(Rev.:2009)

High-Frequency, Low-Cost SMBus Chargers

Maxim Integrated 

High-Frequency,

Low-Cost SMBus Chargers

Table 8. IINPVoltage() (0x3E) (continued)

BIT

BIT NAME

DESCRIPTION

11

IINP Voltage, DACV 6

0 = Adds 0mV of IINP voltage.

1 = Adds 819.2V of IINP voltage to a maximum of 2.20V.

12

IINP Voltage, DACV 7

0 = Adds 0mV of IINP voltage.

1 = Adds 1.6384V of IINP voltage to a maximum of 2.20V.

13

—

Not used. Normally a 8192mV weight.

14

—

Not used. Normally a 16384mV weight.

15

—

Not used. Normally a 32768mV weight.

DC-DC Converter

The MAX17035/MAX17435/MAX17535 employ a synchronous

step-down DC-DC converter with an n-channel, high-side

MOSFET switch and an n-channel low-side synchronous

rectifier. The MAX17035/MAX17435/MAX17535 feature a

pseudo-fixed-frequency, current-mode control scheme

with cycle-by-cycle current limit. The controller’s constant

off-time (tOFF) is calculated based on VDCIN, VCSIN,

and a time constant with a minimum value of 300ns. The

MAX17035/MAX17435/MAX17535 can also operate in

discontinuous conduction mode for improved light-load

efficiency. The operation of the DC-to-DC controller is

determined by the following five comparators as shown in

the functional diagram in Figure 2:

U The IMIN comparator sets the peak inductor current

in discontinuous mode. IMIN compares the control

signal (LVC) against 100mV (typ). When LVC voltage

is less than 100mV, DHI and DLO are both low.

U The CCMP comparator is used for current-mode

regulation in continuous conduction mode. CCMP

compares LVC against the charging current feedback

signal (CSI). The comparator output is high and the

high-side MOSFET on-time is terminated when the

CSI voltage is higher than LVC.

U The IMAX comparator provides a cycle-by-cycle

current limit. IMAX compares CSI to 2V (corresponding

to 10A when RS2 = 10mI). The comparator output is

high and the high-side MOSFET on-time is terminated

when the current-sense signal exceeds 10A. A new

cycle cannot start until the IMAX comparator output

goes low.

U The ZCMP comparator provides zero-crossing

detection during discontinuous conduction. ZCMP

compares the current-sense feedback signal to

500mA (RS2 = 10mI). When the inductor current

is lower than the 500mA threshold, the comparator

output is high and DLO is turned off.

U The OVP comparator. The MAX17035/MAX17435/

MAX17535 incorporate a comparator to check for the

battery voltage 400mV above the set point and, if that

condition is detected, it disables charging.

CCV, CCI, CCS, and LVC Control Blocks

The MAX17035/MAX17435/MAX17535 control input current

(CCS control loop), charge current (CCI control loop), or

charge voltage (CCV control loop), depending on the

operating condition. The three control loops, CCV, CCI,

and CCS are brought together internally at the lowest

voltage clamp (LVC) amplifier. The output of the LVC

amplifier is the feedback control signal for the DC-DC

controller. The minimum voltage at the CCV, CCI, or CCS

appears at the output of the LVC amplifier and clamps

the other control loops to within 0.3V above the control

point. Clamping the other two control loops close to the

lowest control loop ensures fast transition with minimal

overshoot when switching between different control

loops (see the Compensation section).

Continuous Conduction Mode

With sufficient charge current, the MAX17035/MAX17435/

MAX17535s’ inductor current never crosses zero, which

is defined as continuous conduction mode. The regulator

switches at 1.2MHz (nominal) if it is not in dropout (VCSIN

< 0.88 O VDCIN). The controller starts a new cycle by

turning on the high-side MOSFET and turning off the

low-side MOSFET. When the charge current feedback

signal (CSI) is greater than the control point (LVC), the

CCMP comparator output goes high and the controller

initiates the off-time by turning off the high-side MOSFET

and turning on the low-side MOSFET. The operating

frequency is governed by the off-time and is dependent

upon VCSIN and VDCIN.

At the end of the fixed off-time, the controller initiates

a new cycle if the control point (LVC) is greater than

150mV, and the peak charge current is less than the

cycle-by-cycle current limit. Restated another way, IMIN

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