TEA1211HN Philips Semiconductors, TEA1211HN Datasheet - Page 7

• Manufacturer Part Number: TEA1211HN
• Description: High efficiency auto-up/down DC/DC converter
• Manufacturer: Philips Semiconductors

Philips Semiconductors
7.2.3
Refer to Figures 1 and 3. In up-mode the cycle starts by
making P-down and N-up conducting in the first phase.
The second phase N-up opens and P-up starts
conducting. In down-mode the cycle starts with in the first
phase P-up and P-down conducting. The second phase
P-down opens and N-down starts conducting. In PFM
these two phases are followed by a third or wait phase that
opens all switches except for N-down, which is closed to
prevent the coil from floating.
The stationary mode or 4-phase cycle, which only occurs
in PFM, starts with in the first phase P-down and N-up
conducting. In the second phase P-down and P-up
conduct forming a short-cut from battery to output
capacitor. In the third phase P-up and N-down conduct.
The fourth or wait-phase again opens all switches except
for N-down which is closed to prevent the coil from floating.
7.3
The output voltage of the TEA1211HN can be set to a fixed
value by means of an external resistive divider. After
start-up through this divider, dynamic control of the output
voltage is made possible by use of an I
voltage can be programmed from 1.5 V to 5.5 V in
40 steps of 0.1 V each. In case of Power Amplifiers (PAs)
for example the output voltage of the TEA1211HN can be
adjusted to the output power to be transmitted by the PA,
in order to obtain maximum system efficiency.
2003 Oct 13
handbook, full pagewidth
High efficiency auto-up/down
DC/DC converter
V
V
h
l
= Low window limit
= High window limit
Adjustable output voltage
S
WITCHING SEQUENCE
V OUT (typ.)
2%
V h
V l
Fig.5 Spread of location of output voltage window.
maximum positive spread of V FB
2
C-bus. The output
4%
V h
V l
maximum negative spread of V FB
2%
4%
7
7.4
If the input voltage exceeds the start voltage, the
TEA1211HN starts ramping up the voltage at the output
capacitor. Ramping stops when the target level, set by the
external resistors, is reached.
7.5
As a result of too high load or disconnection of the input
power source, the input voltage can drop too low to
guarantee normal regulation. In that case, the device
switches to a shut-down mode stopping the switching
completely. Start-up is possible by crossing the start-up
level again.
7.6
When pin SHDWN is made HIGH, the converter disables
all switches except for N-down (see Fig.1) and power
consumption is reduced to a few A. N-down is kept
conducting to prevent the coil from floating.
7.7
The power switches in the IC are two N-type and two
P-type MOSFETs, having a typical pin-to-pin resistance of
85 m . The maximum continuous input/output current in
the switches is 1.7 A at 70 C ambient temperature.
V h
V l
2%
Start-up
Under voltage lockout
Shut-down
Power switches
upper specification limit
typical situation
lower specification limit
MDB005
Preliminary specification
TEA1211HN