Philips TEA1207T Datasheet

INTEGRATED CIRCUITS

DATA SH EET

TEA1207T

High efficiency DC/DC converter

Product speciﬁcation Supersedes data of 1999 Oct 21 File under Integrated Circuits, IC03

2000 Nov 27

Philips Semiconductors Product speciﬁcation

High efﬁciency DC/DC converter TEA1207T

FEATURES

• Fully integrated DC/DC converter circuit

• Up-or-down conversion

• Start-up from 1.85 V input voltage

• Adjustable output voltage

• High efficiency over large load range

• Power handling capability up to 0.85 A continuous

average current

• 275 kHz switching frequency

• Low quiescent power consumption

• Synchronizing with external 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 TEA1207T 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 Frequency Modulation (PFM), integrated low R switches with low parasitic capacitances, and fully synchronous rectification.

The device operates at 275 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.

CMOS power

DSon

ORDERING INFORMATION

TYPE NUMBER

NAME DESCRIPTION VERSION

TEA1207T SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1

PACKAGE

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Philips Semiconductors Product speciﬁcation

High efﬁciency DC/DC converter TEA1207T

QUICK REFERENCE DATA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

Voltage levels

UPCONVERSION; pin U/D = LOW V

I(start)

input voltage V output voltage 2.80 − 5.50 V

start-up input voltage IL< 125 mA 1.40 1.60 1.85 V DOWNCONVERSION; pin U/D = HIGH V

ENERAL

G V

input voltage 2.80 − 5.50 V

output voltage 1.30 − 5.50 V

feedback voltage 1.19 1.24 1.29 V

Current levels

shdwn

∆I

lim

quiescent current on pin 3 down mode; VI=3.6V526572µA

current in shut-down state − 210µA

maximum continuous current on pin 4 T

current limit deviation I

Power MOSFETs

DSon

drain-to-source on-state resistance

N-type 0.10 0.20 0.30 Ω P-type 0.10 0.22 0.35 Ω

Efﬁciency

efﬁciency upconversion VI= 3.6 V; VO= 4.6 V;

efﬁciency downconversion VI= 3.6 V; VO= 2.0 V;

Timing

sync

res

switching frequency PWM mode 220 275 330 kHz

synchronization clock input frequency 4 6.5 20 MHz

response time from standby to P

I(start)

=80°C −−0.60 A

amb

= 0.5 to 5 A

lim

up mode −17.5 − +17.5 % down mode −17.5 − +17.5 %

L1 = 10 µH

=1mA − 88 − %

= 200 mA − 95 − %

= 1 A; pulsed − 83 − %

L1 = 10 µH

=1mA − 86 − %

= 200 mA − 93 − %

= 1 A; pulsed − 81 − %

− 50 −µs

0(max)

− 5.50 V

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BLOCK DIAGRAM

Philips Semiconductors Product speciﬁcation

High efﬁciency DC/DC converter TEA1207T

ILIM

I/V

CONVERTER

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

TEA1207T

BAND GAP

REFERENCE

MGR665

UPOUT/DNIN

Fig.1 Block diagram.

Philips Semiconductors Product speciﬁcation

High efﬁciency DC/DC converter TEA1207T

PINNING

SYMBOL PIN DESCRIPTION

U/D 1 up-or-down mode selection

input; active LOW for up mode

ILIM 2 current limiting resistor

connection

UPOUT/DNIN 3 output voltage in up mode;

input voltage in down mode 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

U/D SHDWN

ILIM FB

TEA1207T

3 4

LX SYNC

8 7 6 5

MGR666

Fig.2 Pin configuration.

FUNCTIONAL DESCRIPTION Control mechanism

TheTEA1207TDC/DCconverterisabletooperatein PFM (discontinuous conduction) or PWM (continuous conduction) operating mode. All switching actions are completely determined by a digital control circuit which usesthe output voltage level as its controlinput.Thisnovel digital approach enables the use of a new pulse width and frequency modulation scheme, which 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 within the window with higher or lower current capability. This approach enables very fast reaction to load variations. Figure 3 shows the converter’s response to a sudden 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 theinductorcurrentduringa much longer time. As a result, the DC current level is increased and normal 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 ismostdependent on spread, while the actual window size is not affected. For one specific device, the output voltage will not vary more than 2% typically.

In low output power situations, the TEA1207T will switch over to PFM (discontinuous conduction) operating mode. In this mode, regulation information from earlier PWM operating modes is used. This results in optimum inductor peak current levels in the PFM mode, which are slightly larger than the inductor ripple current in the PWM mode. As a result, the transition between PFM and PWM mode is optimum under all circumstances. In the PFM mode the TEA1207Tregulates the output voltage to the high window limit as shown in Fig.3.

Synchronous rectiﬁcation

For optimum efficiency over the whole load range, synchronous rectifiers inside the TEA1207T ensure that during the whole second switching phase, all inductor current will flow through the low-ohmic power MOSFETs. Special circuitry is included which detects that the inductor current reaches zero. Following this detection, the digital controller switches off the power MOSFET and proceeds regulation.

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Philips Semiconductors Product speciﬁcation

High efﬁciency DC/DC converter TEA1207T

Start-up

Start-up from low input voltage in boost mode is realized by an independent start-up oscillator, which 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 0.20 Ω and 0.22 Ω respectively. The maximum average current in the power switches is

0.60 A at T

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, low-frequent cycling 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.

amb

=80°C.

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. Currentlimiting 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.

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 thePFMmode, 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 isnot recommended since instability may occur. There are two exceptions:

• Upconversion: at an input voltage higher than the target output voltage, but up to 6 V, the converter will stop switchingand 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.

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