TEA1202 Philips Semiconductors, TEA1202 Datasheet - Page 8

• Manufacturer Part Number: TEA1202
• Description: Battery power unit
• Manufacturer: Philips Semiconductors

Philips Semiconductors
External synchronization and PWM-only mode
If an external high-frequency clock or a HIGH level is
applied to pin SYNC/PWM, the TEA1202TS will use PWM
regulation independent of the load applied.
In the event a high-frequency clock is applied, the
switching frequency in the PWM mode will be exactly that
frequency divided by 22. In the PWM mode the quiescent
current of the device increases.
In the event that no external synchronization or PWM
mode selection is necessary, pin SYNC/PWM must be
connected to ground.
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:
1. Upconversion: at an input voltage higher than the
2. Downconversion: when the input voltage is lower than
Low dropout voltage regulators
The low dropout voltage regulators are functionally equal
apart from the shut-down mechanism: LDO2 can be
controlled separately by pin SHDWN2, while LDO1 is
controlled by pin SHDWN0 like the DC/DC converter.
The input voltage of each LDO must be 250 mV higher
than its output voltage to achieve full specification on e.g.
ripple rejection. However, the parts will function like an
LDO down to a margin of 75 mV between input and output:
the so-called dropout voltage. At a lower margin between
input and output, the LDOs will behave like a resistor.
2000 Jun 08
Battery power unit
target output voltage, but up to 5.5 V, the converter will
stop switching and the external Schottky diode will
take over. The output voltage will equal the input
voltage minus the diode voltage drop. Since all current
flows through the external diode in this situation, the
current limiting function is not active.
In the PWM mode, the P-type power MOSFET is
always on when the input voltage exceeds the target
output voltage. The internal synchronous rectifier
ensures that the inductor current does not fall below
zero. As a result, the achieved efficiency is higher in
this situation than standard PWM-controlled
converters achieve.
the target output voltage, but higher than 2.2 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.
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Both LDOs are protected from overload conditions by a
current limiting circuit and high temperature
(see Section “Temperature protection”).
Next to normal LDO functions, both regulators can be
switched off or can be used as switches. Each regulator
will act as a low-ohmic switch in the on-state when its
feedback input is connected to ground. When the
feedback input is higher than 2 V, the regulator will make
its power FET high-ohmic. So the feedback inputs of the
regulators can be used as digital inputs which make the
LDOs behave as switches.
Low battery detector
The low battery detector is an autonomous circuit which
can work at an input voltage down to 0.90 V. It is always
on, even when all other blocks are in the shut-down mode.
The detector has two inputs: the input on pin LBI1 is tuned
to accept a 1-cell NiCd or NiMH battery voltage directly,
while the input on pin LBI2 can detect a 2-cell NiCd or
NiMH battery voltage or higher voltage. The detection level
of the input on pin LBI2 can be set by using a voltage
divider between the battery voltage, pin LBI2 and ground.
Hysteresis is included for proper operating. Furthermore, a
capacitor of 10 F (typical value) must be connected
between pin LBI1 and ground when the input on pin LBI2
is used.
The output of the low battery detector on pin LBO is an
open-collector output. The output is high (i.e. no current is
sunk by the collector) when the input voltage of the
detector is below the lower detection level.
Objective specification
TEA1202TS