tea1533p NXP Semiconductors, tea1533p Datasheet - Page 6

• Manufacturer Part Number: tea1533p
• Description: Greenchip Smps Control Ic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Once the drain voltage exceeds the M-level
(mains-dependent operation-enabling level), the start-up
current source will continue charging capacitor C
(switch S1 will be opened); see Fig.2. The IC will activate
the converter as soon as the voltage on pin V
the V
The IC supply is taken over by the auxiliary winding as
soon as the output voltage reaches its intended level and
the IC supply from the mains voltage is subsequently
stopped for high efficiency operation (green function).
The moment the voltage on pin V
undervoltage lock-out level, the IC stops switching and
enters a safe restart from the rectified mains voltage.
Inhibiting the auxiliary supply by external means causes
the converter to operate in a stable, well defined burst
mode.
Supply management
All (internal) reference voltages are derived from a
temperature compensated, on-chip band gap circuit.
Current mode control
Current mode control is used for its good line regulation
behaviour.
The ‘on-time’ is controlled by the internally inverted control
voltage, which is compared with the primary current
information. The primary current is sensed across an
external resistor. The driver output is latched in the logic,
preventing multiple switch-on.
The internal control voltage is inversely proportional to the
external control pin voltage, with an offset of 1.5 V. This
means that a voltage range from 1 to 1.5 V on pin CTRL
will result in an internal control voltage range from
0.5 to 0 V (a high external control voltage results in a low
duty cycle).
Oscillator
The maximum fixed frequency of the oscillator is set by an
internal current source and capacitor. The maximum
frequency is reduced once the control voltage enters the
VCO control window. Then, the maximum frequency
changes linearly with the control voltage until the minimum
frequency is reached (see Figs 5 and 6).
2002 Aug 23
GreenChip
CC(start)
level.
TM
II SMPS control IC
CC
drops below the
CC
passes
VCC
6
Cycle skipping
At very low power levels, a cycle skipping mode will be
activated. A high control voltage will reduce the switching
frequency to a minimum of 25 kHz. If the voltage on the
control pin is raised even more, switch-on of the external
power MOSFET will be inhibited until the voltage on the
control pin has dropped to a lower value again (see Fig.7).
For system accuracy, it is not the absolute voltage on the
control pin that will trigger the cycle skipping mode, but a
signal derived from the internal VCO will be used.
Remark 1: If the no-load requirement of the system is such
that the output voltage can be regulated to its intended
level at a switching frequency of 25 kHz or above, the
cycle skipping mode will not be activated.
Remark 2: As switching will stop when the voltage on the
control pin is raised above a certain level, the burst mode
has to be activated by a microcontroller or any other circuit
sending a 30 s, 16 mA pulse to the control input
(pin CTRL) of the IC.
handbook, halfpage
handbook, halfpage
Fig.6 VCO frequency as function of V
Fig.5 V
V sense(max)
(kHz)
0.52 V
175
f
25
sense(max)
TEA1533P; TEA1533AP
(typ)
1 V
VCO 2
voltage as function of V
level
VCO 1
level
1.5 V
(typ)
V sense(max) (V)
Product specification
175 kHz
MGU509
sense(max)
V CTRL
MGU233
CTRL
.