CWT1541
®
Datasheet
Qi Compliant 15W
Wireless Power Transmitter IC
General Description
CWT1541 can deliver up to 15W as a highly-integrated single-chip wireless medium power transmitter IC. It can
be configured to receive its input power from USB or AC adapter. Our chip integrates a power amp driver, a
precise clock generator for PA frequency control, and communication controllers which use Amplitude Shift
Keying (ASK) and Frequency Shift Keying (FSK). CWT1541 can support multi-coil transmitter with CWP1500
companion PA chip and it also can support precise fixed frequency PA operation with external crystal. Our chip
includes a 32-bit ARM Cortex M0 processor in order to offer high level of programmability according to its
applications. Communication and control units (CCU) can accommodate WPC protocol including fault condition
handling associated with power transfer. The CCU supports the foreign object detection (FOD) extension. Also,
the chip includes over-temperature and voltage protection.
Features Overview
WPC-1.2.4 compliant for MP-A8 medium power
specification
High-efficiency power transfer system
supporting baseline power profile (<5W) and
extended power profile (<15W)
-
Overall system efficiency up to 90%
Input operating voltage of 4.5V to 13V,
supporting USB and AC adapter
Integrated pre-amplify drivers for external
power amp
Support multi-coil transmitter with CWP1500
companion PA chip
Support up to 17 GPIO ports for multi-coil
transmitter
Support precise 127.7kHz fixed frequency PA
operation
Integrated 32-bit ARM Cortex M0 processor
-
SRAM for program memory and data memory
Bi-directional channel communication
12-bit ADC for voltage/current measurement
I2C programmable interface
Foreign object detection
Precise current sensor
Over voltage protection
Over current limit
Over temperature protection
Optional external power amp configuration
128-bit One-Time-Programmable Device
Low stand-by power
QFN 48-pin 6mm x 6mm, 0.4mm pitch
Applications
-
-
Wireless charging pads
Wireless power solutions for Mobile
Applications
Datasheet (REV. 1.0)
Information furnished by CELFRAS is believed to be accurate and
reliable. However, no responsibility is assumed by CELFRAS for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of CELFRAS.
World Wide Web Site: www.celfras.com
Revised 2018-12-24
CWT1541
Qi Compliant 15W Wireless Power Transmitter IC
1. Description for Implementation
Figure 1. CWT1541 Block Diagram
1.1
Overview
A wireless power charging system is composed of transmitter and receiver. In general, wireless power
transmitter will transfer AC power using a power amplifier through a TX inductor coil. Then wireless power
receiver will receive AC power through an RX inductor coil which is strongly coupled with the TX coil. In
transmitter part, power amplifier (PA) will change the DC power to AC power and transfer the AC power to
the TX coil.
Figure1 shows the block diagram of CWT1541 wireless charging transmitter IC. CWT1541 transmitter will
support power transfer up to 15W and it is compliant with WPC 1.2.4 standard. It consists of power amp
driver, step down DC-DC converter, internal LDOs, ADC, 32-bit ARM M0 MCU, SRAM and etc.
1.2
Crystal OSC Driver
CWT1541 employs an internal negative Gm driver in order to drive external crystal. CWT1541 can
implement the precise power transfer frequency by using this crystal oscillator. Some applications often
require accurate PA frequency implementation. With an external crystal, CWT1541 can tune to tens of ppm
accurately.
On the other hand, CWT1541 also supports the internal oscillator. For applications which do not require
the correct frequency, we can lower the BOM by using the internal oscillator.
1.3
Power Amp Driver
-2-
CWT1541 Datasheet (Rev 1.0)
CELFRAS Semiconductor, Inc.
CWT1541
Qi Compliant 15W Wireless Power Transmitter IC
The power amplifier of CWT1541 consists of four external power NLDMOSs and internal driver circuits. The
power amp driver also includes boosting circuits for driving external high side NLDMOS. Each gate control
signal can be adjusted by internal control and MCU.
The power amplifier of CWT1541 converts input DC power to AC power and transfers it directly to the TX
coil. Since power amplifier directly influences the overall transmitter efficiency, the gate control of power
MOSFET switches is very important. The power amp driver of CWT1541 changes its switching frequency and
duty cycle according to the load current and feedback from the receiver.
1.4
FSK Modulator
The Qi extended power profile (EPP) uses two-way communication for power transfer. In the Qi standard,
TX to RX communication is accomplished by frequency shift keying (FSK) modulation over the power signal
frequency.
CWT1541 power transmitter uses FSK modulation for transmitting protocol data to the power receiver.
CWT1541 changes the period of the power transfer signal by counting the internal 60MHz oscillator. The
frequency deviation between the base operating frequency f
OP
and the modulation frequency f
MOD
is
designed according to the Qi EPP standard.
1.5
ASK Demodulator
In the Qi standard, RX to TX communication is accomplished by amplitude shift keying (ASK) modulation
with a bit rate of 2Kbps. CWT1541 power transmitter uses an external peak detection circuit and an internal
comparator circuit for ASK demodulation. The external peak detection circuit include diode and filtering
capacitors and resistors. The ASK demodulator in CWT1541 demodulates the WPC standard 2kHz bi-phase
signal from the power receiver.
1.6
ADC
CWT1541 power transmitter employs 12-bit SAR ADC because it has low power, small area characteristics
and moderate speed performance. ADC monitors important internal voltages and currents and gives the
system information to the digital controller.
1.7
Protection
CWT1541 power transmitter employs various protection schemes in order to prevent system damage.
When the external power amplifier current is too large, the OCL (Over Current Limit) function will limit the
output current. When the temperature inside or outside the chip is too high, the OTP (Over Temperature
Protection) function will shut down the transmitter system to prevent damage resulting from excessive
thermal stress under fault conditions.
1.8
Digital Controller
Digital controller of CWT1541 is composed of a 32-bit ARM Cortex M0 processor, OTP, SRAM for program
and data memory, etc. Digital controller controls all the analog blocks and entire system to perform power
transfer operation according to the wireless power transfer Qi standard. CWT1541 supports the eight GPIO
pins and two of them can be dedicated to I2C interface for communication with external host.
CELFRAS Semiconductor, Inc.
-3-
CWT1541 Datasheet (Rev 1.0)
CWT1541
Qi Compliant 15W Wireless Power Transmitter IC
2. Pin-out and description
Figure 2. CWT1541 Pin Configuration (QFN 48-pin 6mm x 6mm, 0.4mm pitch)
2.1
Pin Description
Name
GPIO21_LED6
GPIO8_LED1
GPIO9_LED2
GPIO14_LED3
GPIO15_LED4
GPIO20_LED5
I/O
General purpose inputs/outputs. These pins can drive large pull-down current
for high brightness LED applications.
Type
Description
Pin Number
1
12
13
28
32
48
CELFRAS Semiconductor, Inc.
-4-
CWT1541 Datasheet (Rev 1.0)
CWT1541
Qi Compliant 15W Wireless Power Transmitter IC
8V high voltage power for OTP programming. During the normal operation,
connect this pin to LDO33.
Internal 3.3V LDO output pin for capacitor connection.
Internal 1.8V LDO output pin for capacitor connection.
Ground for internal digital block.
I
I
O
O
I
External crystal input
DC power input for power transmission.
Internal 5V LDO output pin for capacitor connection.
External crystal output
Active-low enable pin for the entire chip.
Ground for internal reference block.
I
I/O
I/O
Input power supply for GPIO0~7. The operating range of this pin is 1.8~5.0V.
General purpose input/output 0. This pin can be dedicated for I
2
C clock input
for internal register access.
General purpose input/output 1. This pin can be dedicated for I
2
C data
input/output for internal register access.
2
3
4
5
6
7
8
9
10
11
14
15
16
17
18
19
20
21
22
23
24
36
37
25
26,34,38
27,30,33
29
31
35
39
40
41
42
43
44
VPP
LDO33
LDO18
GND_DIG
XTAL_IN
VIN
LDO50
XTAL_OUT
ENB
GND_REF
VDD_IO
GPIO0_SCL
GPIO1_SDA
GPIO2
GPIO4
GPIO3
GPIO5
GPIO6
GPIO10
GPIO7
GPIO11
GPIO18
GPIO19
PA_GH2
VDD_DRV
GND_DRV
PA_GL2
PA_GL1
PA_GH1
PA_BRG
ANA_TEST
EXT_TS
DMOD_VIN
COIL_VIN
TEST_EN
O
O
O
I
O
I
I
I
I
O
I
PA gate driver output for the high side FET of half bridge 2.
Input power supply for the PA drivers.
Ground for PA driver.
PA gate driver output for the low side FET of half bridge 2.
PA gate driver output for the low side FET of half bridge 1.
PA gate driver output for the high side FET of half bridge 1.
PA bridge voltage sensing pin.
Analog test output pin.
External temperature sensor input. Connect this pin to external NTC
thermistor. If not used, connect this pin to LDO33.
Voltage sensing input pin for ASK demodulation.
Q factor Measurement
Digital scan test enable
I/O
General purpose inputs/outputs.
I
O
O
CELFRAS Semiconductor, Inc.
-5-
CWT1541 Datasheet (Rev 1.0)
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