Description
AXPM65611 is a triple DC-DC converter designed to drive AMOLED display panel requiring 3 supply
rails. It integrates an 200mA step-up converter VPOS, an 200mA inverting converter VNEG and an 20mA
auxiliary LDO AVDD. The device is particularly suitable for battery operated products, in which the major
concern is the overall system efficiency. The digital control allows programming the VNEG in digital steps.
Excellent line and load regulation, soft start with controlled inrush current limit, thermal shutdown and
short circuit protection are also integrated.
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
▪ LDO (AVDD)
– 3.3V default or lower of Vin
– 20mA output current
▪ Efficiencies >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
https://www.baitaishengshi.com/uploadfile/2025/0219/20250219103948667.pdf
4 Functional Description
4.1 Overview
AXPM65611 is a high efficiency triple DC-DC converter consisting of 1 step-up converter,1
inverting converter and a AVDD LDO. The VPOS output is fixed at +4.6V and VNEG is
programmable via a digital interface in the range of -1.4V to -4.4V; with default at -2.2V. AVDD
is default set to 3.3V. 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 1 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 -1.4 V 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.
4.3.2 VNEG Transition Time
The transition time (tSET) is the time required to move VNEG from one voltage level to the
next. The transition time is designed for typical 300µs.
4.4 LDO (AVDD)
AVDD is derived from a LDO and can be enabled through the EN pin by connecting to high. In
applications whereby the VIN pin falls below 3.3V, the AVDD output will follow the VIN input
voltage.
4.5 Soft Start and Start-up Sequence
AXPM65611 features a soft-start function to limit inrush current. LDO (AVDD) is enabled when
EN goes high. When CTRL goes high, step-up converter 1 starts with a reduced switch current
limit and 10ms 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 and step-up
converter (VPOS) does not require LDO (AVDD) to be in regulation for it to start.
4.6 VPOS and VNEG Enable (CTRL)
The CTRL pin serves two functions: one is to enable and disable the device VPOS and VNEG,
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.
4.7 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.
4.8 Short Circuit Protection
4.8.1 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 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.
4.8.2 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.
4.9 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.
4.10 Device Functional Modes
4.10.1 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.
4.10.2 Operation with VI ≈ VPOS (Diode Mode)
AXPM65611 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.
4.10.3 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.