tea1553t NXP Semiconductors, tea1553t Datasheet - Page 7

• Manufacturer Part Number: tea1553t
• Description: Tea1553t Greenchip Ii Smps Control Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1553T_1
Product data sheet
7.3 Current mode control
7.4 Oscillator
Current mode control is used for its good line regulation behavior.
The on-time, is controlled by the internally inverted control pin 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 V to 0 V (a high external control voltage
results in a small duty cycle).
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. It then changes linearly with the control voltage until the minimum
frequency is reached (see
Fig 5. The V
Fig 6. The VCO frequency as a function of V
sense(max)
25 kHz
V
voltage as a function of V
sense(max)
Rev. 01 — 3 July 2007
0.52 V
f
Figure 5
(TYP)
LEVEL
and
VCO
1 V
2
Figure
LEVEL
sense (max)
VCO
6).
CTRL
1
(TYP)
1.5 V
GreenChip II SMPS control IC
125 kHz
V
sense(max)
014aaa005
014aaa003
V
CTRL
TEA1553T
© NXP B.V. 2007. All rights reserved.
7 of 27