TCA9534_16 Datasheet, PDF (26/38 Pages) Texas Instruments – Low Voltage 8-Bit I2C and SMBUS Low-Power I/O Expander with Interrupt Output and Configuration Registers

TCA9534
SCPS197B – SEPTEMBER 2014 – REVISED NOVEMBER 2016
10 Power Supply Recommendations
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10.1 Power-On Reset Requirements
In the event of a glitch or data corruption, the TCA9534 can be reset to its default conditions by using the power-
on reset feature. Power-on reset requires that the device go through a power cycle to be completely reset. This
reset also happens when the device is powered on for the first time in an application.
The two types of power-on reset are shown in and Figure 38.
V_CC
Ramp-Down
Ramp-Up
V_CC drops below V_PORF – 50 mV
V_{CC_TRR}
V_{CC_FT}
Time to Re-Ramp
V_{CC_RT}
Time
Figure 38. V_CC is Lowered Below the P_ORF Threshold, then Ramped Back Up to V_CC
Table 8 specifies the performance of the power-on reset feature for the TCA9534 for both types of power-on
reset.
Table 8. Recommended Supply Sequencing And Ramp Rates⁽¹⁾
PARAMETER
MIN MAX UNIT
V_{CC_FT}
V_{CC_RT}
V_{CC_TRR}
V_{CC_GH}
V_{CC_MV}
V_{CC_GW}
Fall rate
Rise rate
Time to re-ramp (when V_CC drops to V_{POR_MIN} – 50 mV or when
V_CC drops to GND)
Level that V_CCP can glitch down to, but not cause a functional
disruption when V_{CCX_GW} = 1 μs
The minimum voltage that V_CC can glitch down to without causing
a reset (V_{CC_GH} must not be violated)
Glitch width that does not cause a functional disruption when
V_{CCX_GH} = 0.5 × V_CCx
See Figure 38
See Figure 38
See Figure 38
See Figure 39
See Figure 39
See Figure 39
1
ms
0.1
ms
2
μs
1.2 V
1.5
V
10 μs
(1) All supply sequencing and ramp rate values are measured at T_A = 25°C
Glitches in the power supply can also affect the power-on reset performance of this device. The glitch width
(V_{CC_GW}) and height (V_{CC_GH}) are dependent on each other. The bypass capacitance, source impedance, and
device impedance are factors that affect power-on reset performance. Figure 39 and Table 8 provide more
information on how to measure these specifications.
V_CC
V_{CC_GH}
V_{CC_MV}
V_{CC_GW}
Figure 39. Glitch Width and Glitch Height
Time
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