NXP Semiconductors
TEA19051BT
USB-PD 2.0/USB-PD 3.0/QC 2.0/QC 3.0/QC 4 (+) controller for SMPS
TEA19051BT All information provided in this document is subject to legal disclaimers. © NXP B.V. 2018. All rights reserved.
Product data sheet Rev. 1 — 13 February 2018
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8.1 Start-up and supply
The TEA19051BT is supplied via the VCC pin connected to the secondary DC voltage of
an AC-to-DC SMPS converter (see Figure 7). To control the primary side controller, this
VCC voltage is regulated via an integrated voltage/current control loop with external loop
compensation and an external optocoupler. This optocoupler is part of the gain loop of
the primary side SMPS controller.
At each start-up and after power-on reset, the optocoupler current is initially zero. So,
the AC-to-DC converter starts up with full output power, resulting in a rapid increase of
the VCC voltage. Due to the low V
CC(start)
level (≈3 V), the TEA19051BT ensures that it
is fully operating before the V
CC
reaches the default initial regulation level. The default
values of the initial regulation level are 5 V and 3 A and they are programmed in the non-
volatile memory (MTP).
At power-on reset, the safe default values, which are read from MTP, are set.
When the V
CC
voltage is below the UVLO level, the external NMOS load switch is off.
When the output is shorted while the load switch is closed, the UVLO is also triggered.
The load switch is then immediately opened and the system restarts after the safe restart
timer.
When the V
CC
exceeds the UVLO level, all circuits, the initial DAC value, and the
resistive divider ratio are initialized. The system regulates the output to 5 V with a limited
output current of 3 A. All these values can be set via the MTP.
To minimize the output voltage overshoot after start-up, an internal 20 mA current sink
is applied to VCC when the VCC voltage exceeds 1.05 × V
o(default)
. The sink current
remains active until the VCC voltage has dropped to below 1.05 × V
o(default)
again.
After the output voltage has stabilized, the load switch becomes conducting and the
system waits for an attach. Before the attach, only the essential circuits are working
which reduces the no-load power to its minimum.
When the voltage on one of the CC pins drops to below the V
IH(Rd)
level, an attach is
detected and all circuits are enabled.
If a protocol is detected, it is allowed to change the voltage and current.
5 V regulation
20 mA
discharge V
CC
reading EEPROM
initialization
1.05 x V
o(default)
UVLO
aaa-023848
Figure 3. Start-up sequence
The TEA19051BT operates on supply voltages up to 21 V. The voltage on the VCC pin is
used to detect an OVP and UVP. The OVP and UVP level are set as a percentage of the
requested output voltage level.
