ML4873 Просмотр технического описания (PDF) - Micro Linear Corporation

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ML4873

Battery Power Control IC

Micro Linear Corporation 

FUNCTIONAL DESCRIPTION

POWER DOWN MODES

The ML4873 operates in either a powered down mode or

a run mode according to the state of the ON/OFF pin

(Table 1). When the ON/OFF pin is high, the IC is in the

run mode and all IC sections are functioning. When the

ON/OFF pin is low, the IC is in the standby mode and

only the µPower 5V linear regulator and 2.5V reference

are on. All gate drive outputs are low. The 5V linear

regulator then provides the power to run the system’s

power management logic. When the BURST pin is high,

and the output is above the lower threshold of the burst

comparator, the IC is also in standby mode, but with the

burst comparator logic also running.

ML4873

BUCK REGULATORS

The two buck regulators (Figure 3) are synchronously

rectifying voltage mode PWM regulators capable of being

used over a wide variety of loads and input voltages. The

use of synchronous rectification improves system

efficiency by reducing the fixed drop associated with the

“freewheeling” diode in conventional regulators. These

regulators also drive all N-Channel power MOSFETs,

significantly improving system efficiency at a low cost.

In order to drive the MOSFET gates adequately, a VGT

supply must be provided which is higher than the battery

voltage by an amount sufficient to provide full

enhancement voltage to the MOSFETs. This can be

generated as shown in figure 2.

TABLE 1. ML4873 POWER DOWN MODES

Mode

On/Off Enable B

Burst

Function

Sleep

0

X

Suspend

1

X

Partial

1

0

Run

Run

1

1

X

5V Linear Reg Only

1

Buck Reg A in Burst Mode 5V Linear Reg on

0

Reg. B Disabled, All Other Functions

Running

0

All Functions Enabled

*Note This figure represents the total quiescent current for the Bust and

5V regulator. Actual current consumed will vary in proportion to load current.

Total Supply

Current

130µA

250µA*

8mA

10mA

5.5

1mA

5

10 mA

4.5

25 mA

4

3.5

3

2.5

2

1.5

4

5

6

7

8

9

VIN INPUT (V)

Figure 1. 5V Linear Regulator Output at low VIN

VGT

OUT1

B1

VIN

B2

OUT2

VIN

RS

0.1

1

VOUT

Figure 2. Generating VGT Bias Voltage

5

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