tea1530t NXP Semiconductors, tea1530t Datasheet - Page 8

• Manufacturer Part Number: tea1530t
• Description: Greenchip Ii Smps Control Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1530T_AT_AP_1
Product data sheet
7.10 Minimum and maximum on-time
7.11 PROTECT and timing input
The minimum on-time of the SMPS is determined by the LEB time (typically 400 ns). The
IC limits the maximum on-time by limiting the driver duty cycle to 70 %. So the maximum
on-time is correlated to the oscillator time which results in an accurate limit of the
minimum input voltage of the flyback converter.
The PROTECT input (pin 3) is a multipurpose, high-impedance input, which can be used
to switch off the IC and create a relatively long timing function. As soon as the voltage on
this pin rises above 2.5 V, switching stops immediately. For the timing function, a current of
typically 50 A flows out of pin PROTECT and charges an external capacitor until the
activation level of 2.5 V is reached. This current source is only activated when the
converter is not in regulation, which is detected by the voltage on pin CTRL
(V
capacitor is not charged, for example, by spikes. An internal MOSFET switch is added to
discharge the external capacitor and ensures a defined start situation. For the
TEA1530AP and TEA1530AT the voltage on pin CTRL determines whether the IC enters
latched protection mode or safe restart protection mode:
Fig 6. Slope compensation
•
•
CTRL
When the voltage on pin CTRL is below 0.63 V, the IC is assumed to be out of
regulation (e.g. the control loop is open). In this case activating pin PROTECT
(V
V
be repeated until the fault condition is removed (safe restart mode).
When the voltage on pin CTRL is above 0.63 V, the output is assumed to be in
regulation. In this case activating pin PROTECT (V
means, will activate the latch protection of the IC. The voltage on pin V
between V
th(UVLO)
PROTECT
< 0.63 V). A (small) discharge current is also implemented to ensure that the
, capacitor C
startup
> 2.5 V) will cause the converter to stop switching. Once V
and V
R CTRL
Rev. 01 — 30 June 2008
VCC
th(UVLO)
will be recharged and the supply will restart. This cycle will
R slopecomp
, but the IC will not start switching again until the latch
CTRL
4
TEA1530T/AT/AP
PROTECT
I sc / t
GreenChip II SMPS control IC
0.63 V
014aaa255
5.6 V
control
detect
> 2.5 V), by external
1
© NXP B.V. 2008. All rights reserved.
CC
CC
drops below
will cycle
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