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產(chǎn)品名稱：AXPM60631 200mA Dual DC-DC Converter for Powering AMOLED Display
型號： AXPM60631
產(chǎn)片介紹：The AXPM60631 is designed to drive AMOLED (Active Matrix Organic Light Emitting Diode) displays requiring positive and negative supply rails The device integrates a boost converter for VPOS and an inverting buck boost converter for VNEG and is suitable for battery-operated products

┄┄┄詳細(xì)介紹┄┄┄

Description

The AXPM60631 is designed to drive AMOLED (Active Matrix Organic Light Emitting Diode) displays

requiring positive and negative supply rails. The device integrates a boost converter for VPOS and an

inverting buck boost converter for VNEG and is suitable for battery-operated products. The digital control

pin (CTRL) allows programming the negative output voltage in digital steps. The AXPM60631 uses a

novel technology enabling excellent line transient performance.

Features

? Operating input voltage range from 2.9V to 4.5V

? Step-up converter (VPOS)

– 4.6V output voltage

– 200mA output current

– 0.5% accuracy (25°C to 85°C)

? Inverting converter (VNEG)

– -1.4V to -4.4V programmable output voltage (-2.2V default)

– 200mA output current

? Efficiency >90%

? Excellent line and load regulation

? Short circuit protection

? Thermal shutdown

Applications

? AMOLED power supply in portable devices like mobile phones, multi-media players, camcorders,

digital still cameras, and wearables.

1 Block Diagram and Application Circuit

2 Pin Description

2.1 Pin Names

2.2 Pin Functions

3. Electrical Specifications

3.1 Absolute Maximum Ratings

3.2 Thermal Data

3.3 ESD and Latch Up

3.4 Electrical Characteristics

VIN=3.7V, CTRL=3.7V, VPOS=+4.6V, VNEG=-2.2V, typical values are at T_A= 25°C (unless

otherwise noted).

4 Functional Description

4.1 Overview

The AXPM60631 consists of a boost converter and an inverting buck boost converter. The

VPOS output is fixed at 4.6V and VNEG output is programmable via a digital interface in the

range of -1.4V ~ -4.4V, the default is -2.2V. The transition time of VNEG output is set to a

default fast timing internally. The device has internal over-temperature protection, under

voltage lockout and soft start which guarantees proper operation during start-up.

4.2 Step-up Converter (VPOS)

Step-up converter uses a fixed-frequency current-mode topology. Its output voltage (VPOS) is

programmed at the factory to 4.6V and cannot be changed by the user.

4.3 Inverting Converter (VNEG)

The inverting converter uses a constant-off-time current-mode topology. The converter's default

output voltage (VNEG) is -2.2V. It can be programmed from -1.4V to -4.4V.

4.3.1 Programming VNEG

The digital interface allows programming of VNEG in discrete steps. If the output voltage setting

function is not required, then the CTRL pin can also be used as a standard enable pin. The

digital output voltage programming of VNEG is implemented using a simple digital interface

(SWIRE) with the timing shown in figure 4.

When CTRL is pulled high, the device starts up with its default voltage of -2.2V. The device

includes a DAC that generates the output voltages shown in table 7. The interface counts the

rising edges applied to the CTRL pin once the device is enabled. According to table 7, VNEG

is programmed to -4.1V since 4 rising edges are detected.

4.3.2 VNEG Transition Time

The transition time (t_SET) is the time required to move VNEG from one voltage level to the next.

It has by default a fast transition time, typical 300µs.

4.4 Soft Start and Start-up Sequence

AXPM60631 features a soft-start function to limit inrush current. When CTRL goes high, step-

up converter starts with a reduced switch current limit and 10 ms later the inverting converter

starts with its default value of -2.2V. The typical start-up sequence is shown in Figure 5. The 2

step-up converters operate independently.

4.5 CTRL

The CTRL pin serves two functions: one is to enable and disable the device, and the other is

to program the output voltage (VNEG) of the inverting buck-boost converter (see Programming

VNEG). If the VNEG programming function is not required, the CTRL pin can be used as a

standard enable pin for the device, which will start up with its default value of -2.2V on VNEG.

The device is enabled when CTRL is pulled high and disabled when CTRL is pulled low. Note

that to ensure proper start up CTRL must be pulled low for a minimum of 200μs before being

pulled high again.

4.6 Under-voltage Lockout

The device features an under-voltage lockout function that disables it when the input supply

voltage is too low for proper operation.

4.7 Short Circuit Protection

4.7.1 Short Circuit During Operation

The device is protected against short circuit of VPOS and VNEG to ground and short circuit of

these two outputs to each other. During normal operation, an error condition is detected if

VPOS falls below 4.1V for longer than 3ms or VNEG is pulled above 85% of the programmed

nominal output by 500mV for longer than 3ms. In either case the device goes into shutdown

and the outputs are disconnected from the input. This state is latched, and to resume normal

operation, VIN must cycle below the under-voltage lockout threshold, or CTRL must toggle

LOW and then HIGH.

4.7.2 Short Circuit During Start-up

During start-up, an error condition is detected in the following cases:

• VPOS is not in regulation 10ms after CTRL goes HIGH.

• VNEG is higher than threshold level 10ms after CTRL goes HIGH.

• VNEG is not in regulation 20ms after CTRL goes HIGH.

If any of the above conditions is met the device goes into shutdown and the outputs are

disconnected from the input. This state is latched, and to resume normal operation, VIN has to

cycle below the undervoltage threshold, or CTRL has to toggle LOW and HIGH.

4.8 Output Discharge During Shut Down

The device outputs can be programmed for Discharge or HiZ during shutdown. Figure 6 shows

the shutdown output control. Device is default programmed for Discharge during shutdown.

4.9 Device Functional Modes

4.9.1 Operation with VIN<2.9V

The recommended minimum input supply voltage for full performance is 2.9V. The device

continues to operate with input supply voltages below 2.9V but full performance is not

guaranteed. It does not operate with input supply voltages below the UVLO threshold.

4.9.2 Operation with VI≈VPOS (Diode Mode)

AXPM60631 features a "diode" mode that enables it to regulate its VPOS output even when

the input supply voltage is close to VPOS (that is, too high for normal step-up operation). When

operating in diode mode the VPOS boost converter's high-side switch is disabled and its body

diode used as the rectifier. Note that a minimum load of ≈2mA is required to have proper output

regulation in diode mode.

4.9.3 Operation with CTRL

When a low-level signal is applied to the CTRL pin the device is disabled and switching is

inhibited. When the input supply voltage is above the UVLO threshold and a high-level signal

is applied to the CTRL pin the device is enabled and its start-up sequence begins.

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