Philips TEA1206T Datasheet

INTEGRATED CIRCUITS

DATA SH EET

TEA1206T

High efficiency DC/DC converter

Product specification
Supersedes data of 1999 Sep 16
File under Integrated Circuits, IC03

2001 Mar 14

Philips Semiconductors Product specification

High efficiency DC/DC converter TEA1206T

FEATURES

• Fully integrated DC/DC converter circuit

• Upconversion or downconversion

• Start-up from 1.8 V input

• Adjustable output voltage

• High efficiency over large load range

• Power handling capability up to 1 A continuous

average current

• 560 kHz switching frequency

• Low quiescent power consumption

• Synchronizes to external 9 to 20 MHz clock

• True current limit for Li-ion battery compatibility

• Up to 100% duty cycle in down mode

• Undervoltage lockout

• Shut-down function

• 8-pin SO package.

APPLICATIONS

• Cellular and cordless phones, Personal Digital
Assistants (PDAs) and others

• Supply voltage source for low-voltage chip sets

• Portable computers

• Battery backup supplies

• Cameras.

GENERAL DESCRIPTION

The TEA1206T (see Fig.1) is a fully integrated DC/DC
converter. Efficient, compact and dynamic power
conversion is achieved using a novel, digitally controlled
concept like Pulse Width Modulation (PWM) or Pulse
FrequencyModulation(PFM),integratedlowR

DSon

CMOS
power switches with low parasitic capacitances, and fully
synchronous rectification.

The device operates at 560 kHz switching frequency
which enables the use of external components with
minimum size. Deadlock is prevented by an on-chip
undervoltage lockout circuit.

Efficient behaviour during short load peaks and
compatibility with Li-ion batteries is guaranteed by an
accurate current limiting function.

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

Voltage levels

UPCONVERSION; PIN U/D = LOW
V

I

V

O

V

I(start)

input voltage V

I(start)

− 5.50 V
output voltage 2.80 − 5.50 V
start-up input voltage IL< 200 mA 1.40 1.60 1.85 V

DOWNCONVERSION; PIN U/D = HIGH
V

I

V

O

input voltage 2.80 − 5.50 V
output voltage 1.25 − 5.50 V

OUTPUT LOOP
V

fb

feedback voltage 1.19 1.24 1.29 V

Current levels

I

q

quiescent current on pin 3 in

VI= 3.6 V 65 75 85 µA

downconversion configuration

I

shdwn

I

LX

shut-down current − 210µA
maximum continuous current on pin 4 −−1.0 A

2001 Mar 14 2

Philips Semiconductors Product specification

High efficiency DC/DC converter TEA1206T

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

∆I

lim

Power MOSFETs

R

DSon

Efficiency (see Fig.5)

η

1

η

2

Timing

f

sw

f

sync

t

res

Note

1. The specified efficiency is valid when using a 330 µFoutput capacitor having an ESR of 0.10 Ω (Sprague 595D) and
a 10 µH small size inductor (Coilcraft DT1608C-103).

current limit deviation I

= 0.5 to 5 A

lim

upconversion −17.5 − +17.5 %
downconversion −17.5 − +17.5 %

drain-to-source on-state resistance:

N-type 0.08 0.14 0.20 Ω
P-type 0.10 0.16 0.25 Ω

efficiency in upconversion
configuration

efficiency in downconversion
configuration

VI= 3.6 V; VO= 4.6 V;
L1 = 10 µH; note 1

=1mA − 86 − %

I

L

I

=10mA − 93 − %

L

I

=50mA − 93 − %

L

I

= 100 mA − 93 − %

L

I

= 500 mA − 93 − %

L

I

= 1 A; pulsed − 87 − %

L

VI= 3.6 V; VO= 1.8 V;
L1 = 10 µH; note 1

I

=1mA − 83 − %

L

I

=10mA − 90 − %

L

=50mA − 91 − %

I

L

I

= 100 mA − 87 − %

L

I

= 500 mA − 88 − %

L

I

= 1 A; pulsed − 82 − %

L

switching frequency PWM mode 475 560 645 kHz
synchronization clock input frequency 9 13 20 MHz
response time from standby to P

o(max)

− 25 −µs

ORDERING INFORMATION

PACKAGE

TYPE NUMBER

NAME DESCRIPTION VERSION

TEA1206T SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1

2001 Mar 14 3

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2001 Mar 14 4

handbook, full pagewidth

BLOCK DIAGRAM

Philips Semiconductors Product specification

High efficiency DC/DC converter TEA1206T

LX

ILIM

4

I/V

CONVERTER

2

CURRENT LIMIT
COMPARATORS

TEMPERATURE

PROTECTION

13 MHz

OSCILLATOR

N-type

POWER

FET

I/V

CONVERTER

sense

FET

GND

P-type POWER FET

SYNC
GATE

5681

SYNC U/D

sense FET

SHDWN

START-UP

CIRCUIT

CONTROL LOGIC

AND

MODE GEARBOX

TIME

COUNTER

DIGITAL CONTROLLER

INTERNAL

SUPPLY

TEA1206T

BAND GAP

REFERENCE

3

7

MGM666

UPOUT/DNIN

FB

Fig.1 Block diagram.

Philips Semiconductors Product specification

High efficiency DC/DC converter TEA1206T

PINNING

SYMBOL PIN DESCRIPTION

U/D 1 conversion mode selection input
ILIM 2 current limit resistor connection
UPOUT/DNIN 3 upconversion output voltage

downconversion input voltage
LX 4 inductor connection
SYNC 5 synchronization clock input
GND 6 ground
FB 7 feedback input
SHDWN 8 shut-down input

handbook, halfpage

UPOUT/DNIN GND

1

U/D SHDWN

2

ILIM FB

TEA1206T

3
4

LX SYNC

8
7
6
5

MGM667

Fig.2 Pin configuration.

FUNCTIONAL DESCRIPTION
Control mechanism

TheTEA1206TDC/DC converter is able to operate inPFM
(discontinuous conduction) or PWM (continuous
conduction) operating mode. All switching actions are
completely determined by a digital control circuit which
usestheoutput voltage level as itscontrolinput.This novel
digital approach enables the use of a new pulse width and
frequency modulation scheme that ensures optimum
power efficiency over the complete operating range of the
converter.

When high output power is requested, the device will
operate in PWM (continuous conduction) operating mode.
This results in minimum AC currents in the circuit
components and hence optimum efficiency, minimum
costs and low EMC. In this operating mode, the output
voltage is allowed to vary between two predefined voltage
levels. As long as the output voltage stays within this
so-called window, switching continues in a fixed pattern.
When the output voltage reaches one of the window
borders, the digital controller immediately reacts by
adjusting the pulse width and inserting a current step in
such a way that the output voltage stays withinthe window
with higher or lower current capability. This approach
enables very fast reaction to load variations.

Figure 3 shows the converter’s response to asudden load
increase. The upper trace shows the output voltage.
The ripple on top of the DC level is a result of the current
in the output capacitor, which changes in sign twice per
cycle, times the capacitor’s internal Equivalent Series
Resistance (ESR). After each ramp-down of the inductor
current, i.e. when the ESR effect increases the output
voltage, the converter determines what to do in the next
cycle. As soon as more load current is taken from the
output the output voltage starts to decay.

When the output voltage becomes lower than the low limit
of the window, a corrective action is taken by a ramp-up of
theinductor current during amuch longer time. Asa result,
the DC current level is increased andnormal PWM control
can continue. The output voltage (including ESR effect) is
again within the predefined window. Figure 4 depicts the
spread of the output voltage window. The absolute value
ismost dependent on spread, whiletheactual window size
is not affected. For one specific device, the output voltage
will not vary more than 2% typically.

In low output power situations, TEA1206T will switch over
toPFM (discontinuous conduction) operating mode.Inthis
mode, regulation information from earlier PWM mode
operation is used. This results in optimum inductor peak
current levels in PFM mode, which are slightly larger than
the inductor ripple current in PWM mode. As a result, the
transitionbetween PFM and PWMmodeis optimum under
all circumstances. In PFM mode, TEA1206T regulates the
output voltage to the high window limit shown in Fig.3.

Synchronous rectification

For optimum efficiency over the whole load range,
synchronous rectifiers inside TEA1206T ensure that
during the whole second switching phase, all inductor
current will flow through the low-ohmic power MOSFETs.
Special circuitry is included to detect when the inductor
current reaches zero. Following this detection, the digital
controller switches off the power MOSFET and proceeds
with regulation.

2001 Mar 14 5

Philips Semiconductors Product specification

High efficiency DC/DC converter TEA1206T

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/DNINis measured to besufficientlyhigh. 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
disablesbothpowerswitchesandthepower 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 Ω and 0.16 Ω respectively. The
maximum average current in the power switches is 1.0 A.

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

Ingeneral,aninput voltage exceeding the specified range
is not recommended since instability may occur. There
are two exceptions:

• Upconversion:ataninput 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 someresistive 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.

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,
switchingbetweenthe on and off statewilloccur.It should
be noted thatin the event of a device temperature around
the cut-off limit, the application differs strongly from
maximum specifications.

Current limiters

Ifthecurrent in one of the powerswitchesexceedsits 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 6