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PWM5031-S View Datasheet(PDF) - Aeroflex Corporation

Part Name
Description
View to exact match
PWM5031-S
Aeroflex
Aeroflex Corporation Aeroflex
PWM5031-S Datasheet PDF : 17 Pages
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If desired, the user can synchronize the oscillator to an external frequency source by coupling a pulse train to the Cset
pin:
Sync Pulse
2nF
24Ω
Cset
To PWM
FIGURE 5 – PWM can be synchronized to external source
with just two additional components.
Operation is similar to the free running case. Cset is alternately charged and discharged by the same current mirrors and
the same comparator and thresholds are used. The only difference is that when a sync pulse is received, the capacitor
voltage is level shifted up and reaches the comparator’s upper threshold voltage before it normally would in the free
running case. If a series of pulses are received with shorter period than that of the free running oscillator, the comparator
will trip in response to the sync pulse and the oscillator will be synchronized. (NOTE: The user must ensure that the sync
pulse does not induce a voltage on CSET that exceeds the PWM5031 voltage rating. If this cannot be guaranteed, a
simple diode clamp to the positive rail should be used to prevent damage to the PWM)
ERROR AMPLIFIER
The main error amplifier is a N-type input folded cascode configuration with a few interesting additions. The positive
input is internally tied to 2.5V derived from the on chip reference. The negative input typically draws less than 1µA and
has a voltage offset of less than 2mV. At 20µA bias current, the amplifier exceeds 2MHz bandwidth and 120dB open
loop gain (see Figure 7).
The amplifier is designed to limit at whatever voltage is applied to the SOFT pin. As mentioned previously, this function
will allow the user to implement a softstart circuit, a controlled turn-on delay, or any number of other useful functions.
Preliminary
SCD5031 Rev B
10
 

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