AFE4403_15 Datasheet, PDF (88/97 Pages) Texas Instruments – AFE4403 Ultra-Small, Integrated Analog Front-End for Heart Rate Monitors and Low-Cost Pulse Oximeters

AFE4403
SBAS650B – MAY 2014 – REVISED JULY 2014
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Case 3: In cases where a high-voltage supply is available in the system, a buck converter or an LDO can be
used to derive the voltage levels required to drive RX_ANA and RX_DIG, as shown in Figure 131.
3.9V
(Connect to LED_DRV_SUP, TX_CTRL_SUP)
LDO
2.2V supply
(Connect to RX_ANA/RX_DIG)
Figure 131. Buck Converter or an LDO
10.1 Power Consumption Considerations
The lowest power consumption mode of the AFE4403 corresponds to the following settings:
• PRF = 62.5 Hz,
• External clock mode (XTALDIS = 1), and
• CLKOUT tri-stated (CLKOUT_TRI = 1).
With the above settings, the currents taken from the supplies are as shown in Table 9. The LED driver current is
with zero LED current setting.
SUPPLY
RX_ANA
RX_DIG
TX_CTRL_SUP
LED_DRV_SUP
Table 9. Current Consumption in Normal Mode
VOLTAGE (V)
2
2
3
3
CURRENT (µA)
490
155
15
55
Enabling the crystal (XTALDIS = 0) leads to an additional power consumption that can be estimated to be
approximately equal to (2 × C_sh + 0.5 × C1 + 0.5 × C2) × 0.4 × f_XTAL, where C_sh is the effective shunt capacitance
of the crystal, C1 and C2 are the capacitances from the XIN and XOUT pins to ground, and f_XTAL is the frequency
of the crystal.
Removing the CLKOUT tri-state leads to an additional power consumption of approximately C_LOAD × V_SUP × f,
where V_SUP is the supply voltage of RX_DIG in volts, f = 4 MHz, C_LOAD = the capacitive load on the CLKOUT pin
+ 2 pF.
88
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