Datasheet
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3 NTC 1
TCOLD
3 NTC 1
TCOLD
COLD
3 NTC 1
TCOLD
3 NTC 1
TCOLD
3 NTC 1
THOT
3 NTC 1
THOT
HOT
3 NTC 1
THOT
3 NTC 1
THOT
R R R
R R R
V 100
R R R
R2
R R R
R R R
R R R
V 100
R R R
R2
R R R
%
%
æ ö
ç ÷
ç ÷
ç ÷
è ø
æ ö
ç ÷
ç ÷
ç ÷
è ø
æ ö
ç ÷
ç ÷
ç ÷
è ø
æ ö
ç ÷
ç ÷
ç ÷
è ø
+
+ +
= ´
+
+
+ +
+
+ +
= ´
+
+
+ +
NTC
VTSB (2.2V)
TS-CTRL
R
3
R
2
R
1
20kΩ
bq51013B
SLUSB62A –MARCH 2013–REVISED OCTOBER 2013
www.ti.com
Synchronous Rectification
The bq5101xB provides an integrated, self-driven synchronous rectifier that enables high-efficiency AC to DC
power conversion. The rectifier consists of an all NMOS H-Bridge driver where the backgates of the diodes are
configured to be the rectifier when the synchronous rectifier is disabled. During the initial startup of the WPC
system the synchronous rectifier is not enabled. At this operating point, the DC rectifier voltage is provided by the
diode rectifier. Once V
RECT
is greater than UVLO, half synchronous mode will be enabled until the load current
surpasses 120 mA. Above 120 mA the full synchronous rectifier stays enabled until the load current drops back
below 100 mA where half synchronous mode is enabled instead.
Temperature Sense Resistor Network (TS)
bq5101xB includes a ratiometric external temperature sense function. The temperature sense function has two
ratiometric thresholds which represent a hot and cold condition. An external temperature sensor is recommended
in order to provide safe operating conditions for the receiver product. This pin is best used for monitoring the
surface that can be exposed to the end user (e.g. place the NTC resistor closest to the user).
Figure 37 allows for any NTC resistor to be used with the given V
HOT
and V
COLD
thresholds.
Figure 37. NTC Circuit Used for Safe Operation of the Wireless Receiver Power Supply
The resistors R
1
and R
3
can be solved by resolving the system of equations at the desired temperature
thresholds. The two equations are:
(3)
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