tea1206t NXP Semiconductors, tea1206t Datasheet - Page 6

• Manufacturer Part Number: tea1206t
• Description: High Efficiency Dc/dc Converter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Start-up
Start-up from low input voltage in boost mode is realized
by an independent start-up oscillator that starts switching
the N-type power MOSFET as soon as the voltage at
pin UPOUT/DNIN is measured to be sufficiently high. The
switch actions of the start-up oscillator will increase the
output voltage. As soon as the output voltage is high
enough for normal regulation, the digital control system
takes over the control of the power MOSFETs.
Undervoltage lockout
As a result of too high load or disconnection of the input
power source, the output voltage can drop so low that
normal regulation cannot be guaranteed. In that case, the
device switches back to start-up mode. If the output
voltage drops down even further, switching is stopped
completely.
Shut-down
When the shut-down input is made HIGH, the converter
disables both power switches and the power consumption
is reduced to a few microamperes.
Power switches
The power switches in the IC are one N-type and one
P-type power MOSFET, having a typical drain-to-source
resistance of 0.14
maximum average current in the power switches is 1.0 A.
Temperature protection
When the device operates in PWM mode and the die
temperature gets too high (typically 175 C) the converter
stops operating. It resumes operation when the die
temperature falls below 175 C again. As a result,
switching between the on and off state will occur. It should
be noted that in the event of a device temperature around
the cut-off limit, the application differs strongly from
maximum specifications.
Current limiters
If the current in one of the power switches exceeds its limit
in the PWM mode, the current ramp is stopped
immediately, and the next switching phase is entered.
Current limiting is required to enable optimal use of
energy in Li-ion batteries, and to keep power conversion
efficient during temporary high loads. Furthermore,
current limiting protects the IC against overload
conditions, inductor saturation, etc. The current limiting
level is set by an external resistor.
2001 Mar 14
High efficiency DC/DC converter
and 0.16
respectively. The
6
External synchronization
If an external high-frequency clock is applied to the
synchronization clock input, the switching frequency in
PWM mode will be exactly that frequency divided by 22.
In the PFM mode, the switching frequency is always
lower. The quiescent current of the device increases
when external clock pulses are applied. In case no
external synchronization is necessary, the
synchronization clock input must be connected to ground
level.
Behaviour at input voltage exceeding the specified
range
In general, an input voltage exceeding the specified range
is not recommended since instability may occur. There
are two exceptions:
Upconversion: at an input voltage higher than the target
output voltage, but up to 5.5 V, the converter will stop
switching and the internal P-type power MOSFET will
be conducting. The output voltage will equal the input
voltage minus some resistive voltage drop. The current
limiting function is not active.
Downconversion: when the input voltage is lower than
the target output voltage, but higher than 2.8 V, the
P-type power MOSFET will stay conducting resulting in
an output voltage being equal to the input voltage
minus some resistive voltage drop. The current limiting
function remains active.
Product specification
TEA1206T