Datasheet

Power Sequencing and Requirements
Power-Up Sequencing
Figure 6. shows the recommended power-up sequence
for the MAX30102.
It is recommended to power the V
DD
supply first, before
the LED power supplies (V
LED+
). The interrupt and I
2
C
pins can be pulled up to an external voltage even when the
power supplies are not powered up.
After the power is established, an interrupt occurs to alert
the system that the MAX30102 is ready for operation.
Reading the I
2
C interrupt register clears the interrupt, as
shown in Figure 6.
Power-Down Sequencing
The MAX30102 is designed to be tolerant of any power
supply sequencing on power-down.
I
2
C Interface
The MAX30102 features an I
2
C/SMBus-compatible, 2-wire
serial interface consisting of a serial data line (SDA) and a
serial clock line (SCL). SDA and SCL facilitate communication
between the MAX30102 and the master at clock rates up to
400kHz. Figure 1 shows the 2-wire interface timing diagram.
The master generates SCL and initiates data transfer on the
bus. The master device writes data to the MAX30102 by
transmitting the proper slave address followed by data. Each
transmit sequence is framed by a START (S) or REPEATED
START (Sr) condition and a STOP (P) condition. Each word
transmitted to the MAX30102 is 8 bits long and is followed by
an acknowledge clock pulse. A master reading data from the
MAX30102 transmits the proper slave address followed by a
series of nine SCL pulses.
The MAX30102 transmits data on SDA in sync with the
master-generated SCL pulses. The master acknowl-
edges receipt of each byte of data. Each read sequence
is framed by a START (S) or REPEATED START (Sr)
condition, a not acknowledge, and a STOP (P) condition.
SDA operates as both an input and an open-drain output.
A pullup resistor, typically greater than 500Ω, is required
on SDA. SCL operates only as an input. A pullup resistor,
typically greater than 500Ω, is required on SCL if there are
multiple masters on the bus, or if the single master has an
open-drain SCL output. Series resistors in line with SDA
and SCL are optional. Series resistors protect the digital
inputs of the MAX30102 from high voltage spikes on the
bus lines and minimize crosstalk and undershoot of the
bus signals.
Bit Transfer
One data bit is transferred during each SCL cycle. The
data on SDA must remain stable during the high period of
the SCL pulse. Changes in SDA while SCL is high are control
signals. See the START and STOP Conditions section.
START and STOP Conditions
SDA and SCL idle high when the bus is not in use. A master
initiates communication by issuing a START condition. A
START condition is a high-to-low transition on SDA with SCL
high. A STOP condition is a low-to-high transition on SDA
while SCL is high (Figure 7). A START condition from the
master signals the beginning of a transmission to the device.
The master terminates transmission, and frees the bus,
by issuing a STOP condition. The bus remains active if a
REPEATED START condition is generated instead of a STOP
condition.
Early STOP Conditions
The MAX30102 recognizes a STOP condition at any point
during data transmission except if the STOP condition
occurs in the same high pulse as a START condition. For
proper operation, do not send a STOP condition during
the same SCL high pulse as the START condition.
Slave Address
A bus master initiates communication with a slave device
by issuing a START condition followed by the 7-bit slave
ID. When idle, the MAX30102 waits for a START condition
followed by its slave ID. The serial interface compares each
slave ID bit by bit, allowing the interface to power down and
disconnect from SCL immediately if an incorrect slave ID
is detected. After recognizing a START condition followed
by the correct slave ID, the MAX30102 is programmed to
accept or send data. The LSB of the slave ID word is the
read/write (R/W) bit. R/W indicates whether the master is
writing to or reading data from the MAX30102 (R/W = 0
selects a write condition, R/W = 1 selects a read condition).
Figure 6. Power-Up Sequence of the Power Supply Rails
V
LED+
V
DD
INT
SDA, SCL
HIGH (I/O PULLUP )
HIGH (I/O PULLUP )
PWR_RDY INTERRUPT
READ TO CLEAR
INTERRUPT
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MAX30102 High-Sensitivity Pulse Oximeter and
Heart-Rate Sensor for Wearable Health