P9038-RNDGI8 datasheet(10/18 Pages) IDT

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P9038 DATASHEET

P9038 August 1, 2016

Description of the Wireless Power Charging System

A wireless charging system is comprised of a base station

(transmitter) and a secondary coil (receiver) positioned

against each other allowing power to be transferred

magnetically. A WPC1 transmitter may be a free-positioning or

magnetically-guided type. A free-positioning type of

transmitter has an array of coils that gives limited spatial

freedom to the end-user, whereas a magnetically-guided type

of transmitter helps the end-user align the receiver to the

transmitter with a magnetic attraction.

The amount of power transferred to the Wireless charging

device is controlled by the receiver. The receiver sends

communication packets to the transmitter to increase power,

decrease power, or maintain the power level. The

communication is digital, and communication of 1's and 0's is

achieved by the Rx modulating the amount of load on the

receiver coil.

To conserve power, the transmitter places itself in a

very-low-power sleep mode unless it detects the presence of

a receiver. Once a receiver is detected, the transmitter exits

sleep mode and begins the power transfer per the WPC

specification.

Input Capacitors

Improper selection of the decoupling capacitor will degrade

the electrical performance of the P9038. The REG_IN and

IN_A to IN_D are the supply rails with nominal operating range

of 4.5V to 6.9V powering the internal drivers and the full bridge

inverter, respectively. At full load, the current through these

pins are both high and fast switching.

Typically, three 10µF and one 0.1µF ceramic capacitor across

the IN_A to IN_D pins are recommended. Similarly, for

REG_IN, a 1µF in parallel with 0.1µF capacitors are sufficient.

Prior to selecting the capacitor, always examine the

capacitor's DC voltage coefficient characteristics as the value

of the capacitors will decrease due to capacitance-to-applied

voltage characteristics of the commonly-used ceramic

dielectrics. For example, a 22µF X7R 6.3V capacitor's value

can actually be 6µF when operating at 5V, depending on the

manufacturer. Typically, 10V- or 16V-rated capacitors are

required. It is typically best to select these capacitors with a

voltage rating from two to two and half times the expected

applied voltage.

For optimum device performance, the decoupling capacitors

must be mounted on the component side of the PCB, and

also, located as physically close as possible to the related

power pins and power ground (PGND).

LDO5V & LDO2P5V

The LDO5V and LDO2P5V are 5V and 2.5V linear regulators

designed to power the internal circuitry. They can support

maximum of 10mA and 5mA of load current, respectively. To

stabilize the regulators, a 1µF capacitor from the output pin to

GND must be connected.

The GATE pin and associated MOSFET shown in Figure 2

below provide protection to the P9038 from input over-voltage

events and control current inrush. Both of these features are

described in subsequent sections of this document.

Figure 2. Input Voltage Support Range (UVLO)

Full-bridge MOSFET Drive and MOSFET

Current Sense

The P9038 incorporates an integrated full-bridge inverter.

Each half-bridge contains a high-side current sense block that

is used for control and for peak current protection. For EMI

reduction purposes, the switching rising and falling rates of the

internal MOSFETs are controlled.

Input Over-voltage Protection and In-rush

Control

The P9038 offers additional protection in the event of input

voltage transients and the programmable soft start time to

minimize the inrush currents. The P9038 is powered from a

VBUS input which may be subjected to voltages above 5.5V

under normal operation. The P9038 is designed to support

voltages as high as 27 V on this input. An external OVP

MOSFET is used to isolate pins that would be damaged by a

27 V transient on the VBUS input. The OVP MOSFET has a

second function: limiting inrush current from the VBUS line

during startup. This is necessary due to the USB inrush

specification and the large total effective capacitance (~40µF)

on the REG_IN and IN pins of the IC.

P9038

REG_IN

CREG_IN

LDO5V

CLDO5V

GATE

VBUS_SNS

ADAPTOR

4.5 V Min

25 m



To Inverter

IDC = 1.5 A

4.5 V - 25 m

 * 1.5 A =

4.46 V



To IC

IDC = 45 mA

For Demonstration Purposes Only

Not All Connections Shown

Not To Scale

4.46 V – 5

 * 45 mA = 4.23 V

LDO2P5V_IN

LDO2P5V

UVLO

BAND

GAP

LDO5V

INVERTER

& MCU

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